GMC Sierra 1500 Extended Cab Pick-up

2007 GMC Sierra 1500 Extended Cab Pick-up Engine   

My engine become more difficult to start. It will start out as though the starer is dragging and then start spinning fast and back to dragging again. I replaced the battery and cleaned the terminals. The truck is 1997 GMC Z71 5.7 automatic. It has 174,000 mile on it. The oil was recently change and it still registers full. darkhoss70@gmail.com

The truck is a 1997. All my fluid levels are fine. I live in STL and weather here the last couple of months has been wet and snowy. The slow starts have been occasion with the exception of Saturday and today Monday.

One common problem on these trucks is a leaking fuel injector/pressure regulator/fuel line. To check, when you park the truck, remove the fuel pressure test cap, release the fuel pressure. Check the next day to see if it spins freely. If it does, then the intake will need to come off for component replacement.

I'm not real savy on these trucks. Can you give me an ideal of where the fuel pressuse regulator test cap is located on tthe intake, front rear or left/right side?

The fuel pressure test port is on the stainless steel fuel line, between the engine and the firewall.

2005 GMC Sierra 1500 Extended Cab Pick-up Electrical / Lighting Systems   

these problems are random don't occur all the time but ussual pass with each day and have been apparent in the last two weeks. Temp gauge not functioning a few seconds after start up warm or cold(works on and off). Speedometer sticks, fails, sticks at 40mph or indicates 40mph over current speed. Truck switched to 4low after switch from park to drive(truck has 4wd on fly button, did not press) this has happened 3 times now and the last time it was very hard to get it to switch back to 4h or to 2h, radio had no power(only once). The first time I noticed the speedometer running incorrectly on the highway, I pulled over and noticed it was stuck at 40mph, I placed it in park, shut the engine off, and it would not restart. Electrical power was present, no buzz, no clicking, seemed as if it was stuck in gear. Thinking it was maybe a computer glick, dis/reconnected battery and started right up(the engine was shut off for about 20min). truck has 97,000 miles and all maintance is up to date. Any suggestions on what to check or steps to take from cheapest to most expensive to find the problem. thx

The printed circut on the back of the instrument cluster or the plug itselef may be in question.Its not easy to get to without removing trim panels.If you want to try answer back and I'll try and work you thru.

2004 GMC Sierra 1500 Extended Cab Pick-up Fuel System   

Runs for a while and just looses power. my start again and may not after awhile. Have replaced fuel pump, filter, throttle position sensor, coolant temp sensor and hasnt solved problem. will start with starting fluid and run fine as long as u dont get off of gas. injectors wont shoot gas at initial starting when key is turned but with starting fluid it starts and injectors shoot gas for a while and stop and goes dead

I am hoping that you are scanning for codes? wise you might be replacing many sensors needlessly.
I believe it might be the crankshaft position sensor. I believe there may have been a factory recall for them, you might want to check that.

2002 GMC Sierra 1500 Extended Cab Pick-up Electrical / Lighting Systems Malfunction Happens sometimes No pattern

The truck is actually a 1500HD crewcab.
Problem: The truck starts, the Message center shows the battery indicator, which stays on. The odometer, shifter position indicator, dash lights, auto transfercase, heater controls and wind sheild wiper controls, fuel guage, and the transmision temp guage do not work.

When it happens: Mostly when I try to start it with the remote starter. (Astrostart) But when I try with the remote starter, it doesn't start then, but then it will start with the key. But then the above problem happens. I have caused the same thing to happen 2 times by turning the windsheild wiper/wash knob.

I have got the system to come back on a couple of times by turning the heater knob and 1 time by turning the wiper/washer knob.

Extra's: The truck will drive fine, but the transmition will go into over driver at slow speeds once in a while. I did try un hooking the battery, but didn't help this time to turn the system back on.

My thoughts: Possibly the remote starter causing problems? I have tried turning it off and even took the fuses out and didn't help. It seams at times it only takes an electrical surge from the heater knob or the wiper/washer knob to get it to go on and off. It has been off for the last 2 days and have driven the truck a couple of times.

Thanks

Rod Gravel

Hi;
Disconnect the whole thing! Sounds you have a crossed wire. Even though you disconnected the the fuse, does not mean that all power was shut off to it. Les.

Thanks,

I will try to get it into someone to check it out today.

"Hi,
Unfortunatly I don't have anyone around that does astrostart. What I was wondering (before I get it replaced) is that it has been in the truck for over 3 years now and only had the problem once or twice before I got the truck (bought it from friend about 6 months ago)and in the last 3 months or so, it has steadly got worse. Then today I started it up with the key and about 30 seconds later everything came on. Then after being downtown and using the signal light it went off again. Just wondering that if a wire was crossed, wouldn't I have seen the problem a long time ago?

Thanks"

Hi;
Maybe and maybe not. The only way to check it out is have it tested. It can be a wire causing a bad connection ( crossed wire ) or the controller itself. Les

2000 GMC Sierra 1500 Extended Cab Pick-up Heating / Cooling System Malfunction When idling Always

when fan is on and recirc button is pushed a/c comp.comes on when fan is on and blend button is turned to floor only a/c comp. comes on with climate control off and driving air flows through cab unless you push the recirc. button other than these 3 questions the only thing i know to do is replace the c.c module in the dash with a new one any help much app Thanks Todd

Todd, I would check with the owners manual, or even go to a dealer and look in the climate control section, to see whta actions take place when those combinations are used, IE: a/c comp. comes on. To me this sounds normal. I may be wrong, but I do not have a manual with me on this matter. Unless some things have changed, if I am not mistaken, GMs fans do not turn off completely unless the climate control system is turned off and the times you said the A/C comes on,seems normal to me as well. Please let me know what you find out. Good Luck!!

Can you please settle up your account with me and All-Parts so the account can be closed. What has happened to your problem? Thanks in advance

2000 GMC Sierra 1500 Extended Cab Pick-up Electrical / Lighting Systems   

For Law Enforcement purposes, I need to disable chime/buzzer that sounds continually when I try to run AM/FM radio or parking lights while engine is off AND DRIVER DOOR IS OPEN.

Or at least program it to do a one-time reminder chime and then shut up, for ANY function that makes it chime. Maybe even reduce the frequency so it chimes once every 5 or 10 minutes instead of 2-3 times per second.

On my previous 99 Chev CK1500, I easily found the buzzer module & removed it. However, on this GMC, the chiming seems to emanate from a larger, multiple-use-multiple-wired module above brake pedal.

Sgt. Ruben Rodriguez, NCSD
361/887-2277 Office
Corpus Christi, TX

Hello, I hope to have your answer tomorrow the 9th. Back to you ASAP. I am in the Oklahoma City area and will get with the GMC dealer for help you can count on.

Roger

The 2000 with the chime is the new body style. (My old 1999 with the buzzer was the old body style)

I'll go forward with the new body style as a base. The uplink states that there is a old and a new body style in the model year 2000. Interesting, more on this tomorrow.

Do you have a FAX number I may send you some wiring diagrams to? They may prove useful to you.

Roger

Yes, but only fax during business hours to Attn: "Sgt. Radar Rodriguez" at [redacted] . Thanks.

Are weekend business hours the same as weekdays for your office?

Roger

Sgt., A FAX is on the way for you to identify the circuits you want to disable on your GMC. Key warning and driver's door switch input are easily seen. I'm still thinking about the seatbelt and exterior "lights on" warnings. Are these critical too? Reprogramming the module is not an option/feature on the 2000 model. It is an option on newer models.

I wondered if you would want to put a panel of custom toggle switches in line for the circuits you desire to disable so you could easily select circuit operation?

Roger

Hello, Did the FAX I sent come through clear and usable?

Roger

Sorry, was off yesterday. Yes, received fax fine day before yesterday, it is mostly legible. I see 2 places I could try to experiment (door ajar switch & key-in-ignition sensor) but was hoping to find actual chime (buzzer) wire.

I reminded myself a few nights ago that the other related problem was chime sounding when turning parking or headlights on IF engine is not running.

No rush while I try to find time to locate the above mentioned wires. Thanks.

You are on track with the door ajar and ignition key circuits. I also want to find the answer concerning the lights on warning.

There is no wire for the chime as it really is inside the module itself. I don't have schematics specific to the audio device itself to recommend action. The module will have to be opened for an evaluation to determine how to disable only the audio device. Do you know any good circuit board technicians? (computers, television, etc?)

Notice the fuse that powers the park light input and another one that powers the seatbelt warning. Can you pull these fuses and see what that will do? You may not have park lights if you do, I can't tell and I don't have a vehicle to experiment on.

Still looking into it,

Roger

I just remembered something someone told me many weeks ago that I forgot... How can I get a list of code-sequences to reprogram the vehicle's computer? I know that to reset the "Change Oil" display on the multi-purpose indicator, I have to turn the key to on without starting the engine and then depress (to the floor) the gas pedal 3 (or 5?) times.

That one was in the owner's manual but it is said there are many others not described in the manual. Maybe the options I want are among those unlisted secret codes?

Once again, take your time please, no rush.

I'll see what I can find out. I've been told the year 2000 computer is not reprogrammable, but newer models are. Maybe I can find that in writing.

If your body computer can be programmed it will take a GM TECH II SCANNER to do it. Normally this $2700.00 scanner is found only at a General Motors dealership. Got any local friends you could ask to attempt this proceedure?

Roger

Roger

Guys around here say your Sierra Body Module cannot be programmed as you desire to silence the warning audio.

Consider opening the module and see if you can disable from within.

Roger

Okay, I give up. I'm considering opening the module. I'm afraid if I disconnect it the truck will never start again. Or maybe if I unhook it wrong, I'll break a peg or hook or other attachment. Any pointers from the experts on this module? I AM skilled with soldering iron and am an Amateur Radio Licensed Tech. Just not with newfangled cars/trucks & hidden screws & hidden latches. :)

There is no magic here. The trick is to avoid an electrostatic discharge to the circuit board. Touch truck metal before you remove the module. The connectors are rugged and if you release the retainers, wiggle and pull you'll be fine.

The body module does not run the powertrain and your truck should not have problems restarting.

When you are ready to reinstall the module touch its' case to truck metal to ground any static electricity and you will be grounded too because you are holding the module in your bare hand.

Go for it, you can do it!

Roger

Good morning Sgt. Have you silenced the warning audio on your truck?

Roger

Hello, Still need help here?

Thanks,

Roger

2000 GMC Sierra 1500 Extended Cab Pick-up Drive Train / Driveline   

My Electronic 4 wheel drive will not engage. Any option I pick on the switch will not work engage the transfer case. The light on each switch blinks but will not go solid and 4 wheel will not engage. Auto 4 wheel, at any speed, 4 wheel in nuetral, and 3 low in nuetral rolling at about a couple miles an hour.

The encoder motor on the transfer case is the common failure.

Did the problem come on at all once?

I don't often use the 4 wheel, so when I tried to use it it had this issue. Not sure what you mean my all at once.

Any chance it could be the electrical connector on the motor? I haven't crawled under the truck yet.
Is there a vacuum line somewhere? Someone told me it might be a broken or leaky vacuum line.

Hi,

By all at once I was wondering if anything else led to the problem, such as noise, etc. Or if the problem was intermittent at any point.

Do thoroughly inspect the connectors to the motor. Disconnect and inpsect for trouble.

1997 GMC Sierra 1500 Extended Cab Pick-up Electrical / Lighting Systems   

Just installed a re-bilt trans in 1997 4 whl dr Sierra New Neut. Safe. Swith. The truck will go into park w.o. light but will not start. Truck will start in Neut. and move thru N,R,123 with light. Will not move as if Brake or Trans holding. Have adj. neut. safe swit. but it is no better. Have checked all harness plugged in. Don't know what to do next.

Check the actual shifter linkage adjustment, as there is an adjustment for column shifted trucks.
Ensure the switch is the correct one, I have lots of experience getting wrong parts!
Try starting and shifting with linkage disconnected first.

1996 GMC Sierra 1500 Extended Cab Pick-up Engine Lagging When accelerating No pattern

I have a 96 gmc 1500 4x4 z71 with 103,000. When accelerating or going up hills the engine sounds loud, like it is working real hard or towing when it is not towing. When towing the engine gets real hot and seems to have less power than it used to. Has trouble towing over just small hills, sometimes feels like it won't make it over.

Does the check engine light come on while the engine is running?

When was the last complete tune-up?

Does the engine smell hot or does the temperature on the gauge rise above normal?

Is the transmission slipping or is this purely an engine performance issue?

the check engine light does not come on while the engine is running. The last tune up, spark plugs replaced etc was at 83,000 in sept 04. The radiator was flushed and transmission fluid changed at 101,000. The engine does not smell hot, but when towing over even small grades, the temp gauge reads up to 210 or slightly over, when it never used to run that hot, unless it was a serious long grade. When not towing the temp gauge stays in normal range, but still sounds like it working hard and has less power. The transmission does not seem to be slipping, so I guess it is a performance issue.

Make sure the thermostat is okay.

The next thing I'd check is for a restricted exhaust (IE- a plugging catalytic converter).

1996 GMC Sierra 1500 Extended Cab Pick-up Drive Train / Driveline   

we just had the transfer case rebuilt and now they are telling us that it won't go into hi four wheel drive and won't drive and that the accuator is bad so we went to get and accuator and waiting to hear about that but he also said that it might be the four wheel drive computer anyone have any ideas about that?

The actuator is a common part to replace.It is essentially an electric solenoid.
The computer is seldom a problem though if the solenoid had a short circuit it might damage the comp. With the solenoid I prefer new, with the computer, I prefer used.

1996 GMC Sierra 1500 Extended Cab Pick-up Fuel System   

Need to shoot starter fluid into intake system to start on a warm day in the 80's. Once the engine is warm it starts ok. Is that a fuel pump problem? aloha

I have replaced the cap, rotor, plugs, wires, 02 sensors, thermostat sensor and there are no error codes when we check the system. The problem is I have to drive serveral miles to the mechanics place to check it out. The operating temp is indicationg 150 but when we shoot it will a infrared gun it shows 190f.

Hello, It could be a fuel pump problem as in low pressure, or a restriction like a dirty fuel filter resulting in poor flow volume.

When the key is turned to ON and before you turn it to START, do you hear the fuel pump run for two seconds to pressure up the fuel rail?

Roger

when I turn on the key and listen at the gas tank there is a slight whirring or hissing sound at the tank. When we did it several times I decided to try and start the engine it started up. It has been siting there for at least two hours cooling down.
Ken

I forgot to mention that I have power when I drive but not like it used to be so I am guessing a bogging down under full power could be part of the same problem?

Ken

There are some things fairly easy to do to begin diagnosis. Changing the fuel filter, inspecting the air filter, testing the fuel pressure...checking the fuel pressure regulator operation.

When you consider loss of power a compression test, checking for exhaust restriction, power flushing fuel injectors are areas that may provide some clues.

Roger

Thanks Rodger I will give it a look.

Aloha,
Ken

I'll look for your next message with your findings.

Roger

1996 GMC Sierra 1500 Extended Cab Pick-up Fuel System   

I stopped and started my truck all day with no problems. Several hours after I returned home for the day, I tried to start the truck but the gas would not go through to the engine. When I turned the ignition, it turned over and the noise was made as if it was about to start, but it will not start. I stopped trying after a few times to avoid flooding the engine. I looked under the hood for dampness around the spark plugs or loose spark plug wires, but found neither. I have about a half tank of gas in the truck. This just happened all of a sudden. Any ideas before I have it towed to the dealer? Thanks.

Sounds like the fuel filter is plugged or (more likely) the fuel pump has quit.Have someone listen for a hum at the gas cap opening (cap off)when you turn the key to the run position.Try adding a few tablespoons of gas to the throttle body to see if it momentarily starts. If it does, this would verify a fuel pump problem

1996 GMC Sierra 1500 Extended Cab Pick-up Electrical / Lighting Systems   

driving lights do not work, green light comes on with ign. on, green light turns off with headlights on

Hello, Please clarify....are we talking about the daytime running lights?

Have you removed the bulbs to see if power is present at the bulb connectors?

Roger

My headlights come on, on bright, that is the two inner ones. When i press the e-brake the green light goes out. The fuse is good. and I changed out a little relay which I took out of another vehicle that was working, this is located by the left foot in an electical box

OK, so no low beam headlights? Have you removed the bulbs to see if power is present at the bulb connectors?

Roger

yes, the bulbs on my bright lights where daytime running lights normally light up are working. I hear there could be a resister somewhere. So could you please tell my why my daytime running lights wont work. I think I have gave you enough information now. When the ignition is turned on the daytime running lights indicator comes on , and when I switch the headlights on the indicator comes off as normal. For I have another vehicle I can compare with.

You haven't stated if you have power at the bulbs when DRLs are expected. I have asked you twice....Do you have/want a wiring diagram?

There is a daytime running light relay controlled by the daytime running lights module. The relay gets it's power from the DRL-Fog Fuse #15 (20 amp) in the IP Fuse Block.

The DRL indicator on the instrument panel gets it's power from the Gages Fuse #4 in the IP Fuse Block.

There is no resistor in the circuit. Do you have an Owner's Manual with the legend for the under hood fuse relay block? I believe the DRL Relay is there and could be the problem if you do not have power at the connectors for the bulbs when DRLs are expected.

Roger

1996 GMC Sierra 1500 Extended Cab Pick-up Brake System   

Hi, I applied the brakes & the pedal went all the way to the firewall, no braking at all. I didn't have a broken brake line or leak. After replacing the Master cylinder, the brakes are still soft. Thought it might be debris in the ABS, so I flushed & refilled the system & still kinda soft. Could the problem be in the control unit? Kinda at my wits end, thanks.

If it was a reman unit. the master might br defective.It might be bypassing internally. New ones are usually ok. With ABS, it sometimes takes repeated bleading, or 'pressure' bleeding to get it right.

1996 GMC Sierra 1500 Extended Cab Pick-up Engine   

upon start it runs and idles perfectly. revs clean and returns to idle quickly and accurately with no wavering. after about a minute, the idle starts to drop, the engine skips, and black smoke starts to come out the exhaust. then it revs slowly and it never returns acurately to idle.
if you shut off the engine and re-crank it, it will then idle and rev perfectly again for a minute or so. also if you put it in gear during this time, it will accelerate strong and clean with no problems. after about a minutes time, the hiccups and black smoke begin. rough idle and idle drops from 950 to about 700-800 and fluctuates.

Hello, Please try unplugging the MAP Sensor and see if the value substituted by the computer allows the engine to run. If so, replace the MAP Sensor.

What engine please? Are diagnostic codes present?

Roger

its a 262 cu. in. or 4.3 litre v-6 vortec. i have no codes available but, i have had someone mention the map sensor. ill give that a try. which one is the map sensor?

The MAP Sensor has a three wire connector and a vacuum hose connection. The wire colors are Lt Grn, Blk, and Gray. The sensor is located top right center of the engine near the fuel injectors.

Roger

thx roger ill try that.

I'm interested in the results. Update when you can.

Roger

hey Roger, i tried the map sensor disconnect trick. there was no change. it really acts as if the computer is retarding the timing. ive experienced this before with a diff. vehicle with manual timing adjust when the distributor was a tooth off.
the vortec however has no manual adjust. all computer. i checked and rechecked. with #1 at tdc on the compression stroke, the rotor button points DIRECTLY at the embossment numbered "6" inside the base of the distributor which, is what the manual indicates as the tdc mark for vortec 6 cyl when setting the distrubutor timing. also its directly under the pin which will fire the number one plug.
do you think maybe there is a timing sensor that is bad? i know of one on the bottom of the timing cover. is there another? and should i go that route?

No, I wouldn't go for a timing issue. I am interested in the coolant temp sensor accuracy. I believe the engine is getting too much fuel. This could be a sensor or even a fuel pressure regulator problem.

But to check the coolant temp sensor A diagnostic scanner will be needed. A code reader won't do the job. Do you have access to a scanner?

Roger

no sir. no access to a scanner. the temp guage on the dash has always read cool. i always assumed it just didnt work properly. where is she located? ill go ahead and change it since i know it has always been a problem.

i nursed it to the advance auto. the computer read a bad map sensor and a bad manufacturer auxillary emmission control sensor. whatever that is. and gave a code of p1406. i replaced the map sensor and the symptoms are still the same. i bought a temp sensor anyway since i already know the original is bad. however, it has always been bad so im not sure its contributing to the problem. when she cools off ill replace it. until tomorrow. thanks. jeff

Are you confident the engine actually warms up properly? Could it be that the thermostat is stuck open and the result is a cool temp reading?

I'll look up this code P1406.

Roger

Hey! The GM Code P1406 refers to the EGR Valve Pintle Position Circuit. I don't know where this business of an aux emmission control sensor came from.

Remove the EGR Valve and turn it upside down. Has the pintle stuck? If you press in on the pintle will it snap closed when you release it, or does it seem to be coked up and binding?

The EGR Valve pintle can be cleaned with a spray carb/choke cleaner. I do this in a well ventalated area away from any open flame. Do not use a metal brush as scratches cause trouble.

Get the pintle and the bore both clean of all deposits. We want the pintle to move freely all the way in and out without binding. Protect your hands and eyes from this chemical.

Remount the EGR Valve with a new gasket if the old one ruined when removing the part.

Retest engine performance.

Roger

hey roger, i cleaned up the egr valve and replaced it. it was a bit crusty and may have been sticking. i cleaned er good. the pintle is actuating smoothly.
no error codes as of yet however, the symptoms are the same. just for the heck of it i took it out on the street to run it again. it is completely sick and wont rev under load until you go wide open throttle. then it picks up like she used to and runs clean and quick almost as if it were a four bbl that was running on the secondarys only. what do ya think; throttle position sensor, something like that?
injector maybe. are there 2 sets of injectors?
thanks for your help. i think we are narrowing down the problem. thx. jeff

Jeff, May I have your email address please? I want to send you a couple of list of things to consider when trying to diagnose a sluggish engine and poor idle quality.

Roger

sure thing. its [redacted]

Sorry for the delay. I had tires put on my kids truck and it took Wal-Mart 5 hours!

Check your inbox and if not seen there check also your spam/junk folders for subject line CHECK LISTS.

Roger

thanks man. ill give er a look when i get home. now the darn thing wont crank at all. no spark coming from the coil.
i replaced the throttle position sensor. the return spring inside it was broken. dont know if that had anything to do with it working or not but, i went ahead and changed it anyway. cranked the truck. same symptoms. the tack went jiggly for a minute. then she died. 2 mins. later she cranked up but died. now it just turns over.
fun stuff. ill check my email.
thx roger. Jeff

If you disconnect the coil wire from the distributor cap will spark jump from the coil wire to ground when the engine is cranking?

Roger

it was completely dead. no spark. i figured out the problem though. the plug attached to the sensor on the timing cover had a terminal that was loose. so i took the plug apart, cleaned it, made sure the prongs were gonna grab good and plugged er back up. it fired right up.
still got the same rough running issue though. so, i broke down and bought a brand new egr valve and installed it. still the same symptoms.
tomorrow someone is going to come by with a scanner or something. he says this will undoubtedly tell us what the problem is. i hope so.
i really appreciate you trying to help me troubleshoot this thing. im beginning to think either the timing gears are not lined up properly or the distributor is afoul or something like that.
ill keep ya posted.
thx. jeff

Let me ask you to stop throwing parts at this bad boy. We need to diagnose the problem properly and not fix it by accidentally affording the right guess.

I don't believe you would allow a technician such priveledge.

Roger

youre absolutely right. ive got someone coming tomorrow with a scanner thingy. he said it will diagnose the problem.
lets hope. thanks again for your help and ill keep ya posted. if you have any more ideas though, please drop me a line here.
talk at ya tomorrow. jeff

Any news here? Please update when you can.

Thanks,

Roger

1995 GMC Sierra 1500 Extended Cab Pick-up Drive Train / Driveline   

This problem is both electrical and drive train, my tach and speedometer quit from time to time and when that happens I also do not have 1st gear or overdrive. I have to manually shift to 2nd to start and then to 3rd. At the same time my gearshift indicator goes away. The next time I start it it might work fine, it is very intermittent

This really sounds like the VSS (vehicle speed sensor).

Does the check engine light come on when the problem occurs, or at anytime while the engine is running?

no not recently, however I checked the codes and they were 66, 67, 81, 82 and 83 which all have to do with the shift solenoid circuits and the torque converter solenoid circuits, but yet when the speedometer and tach work all the gears work fine.

With the engine idling, wiggle the key (not enough to engage the starter or shut the engine off) to see if you can duplicate the tach dropping out.

I have done that and it doesn't seem to make any difference when it is not working, I haven't tried it when it is working. Today for instance it hasn't worked at all. The next time it works I will try that. Have you ruled out the Speed Sensor?

Probably, I overlooked the part about the tach dropping out simultaneously.

Now we are try to see if the problem is with the ignition switch, rather common on GM's.

It is the Ignition switch, checked the power to the fuse for the transmission and no power there, isolated the wire up by the switch and no power from the switch. Thank you for your help. When we turn off the codes and start the engine the Tach works the first time as I guess because the codes have not reset yet when we first start the engine.

Good work, not easy to isolate.

I'm not sure why the tach works fine after resetting the computer.

1995 GMC Sierra 1500 Extended Cab Pick-up Engine   

350 throttle body, code 43. We have replaced plugs, wire, cap, rotor, module, tps, knock sensor, map sensor, coil, ox sensor. Idle in gear is about 50 to 100 rpms off and causing engine to die an is becoming hard to start. Check engine light is on

Hello, Do you need a wiring diagram? I can email one to you if you'll tell me the email addy to send it to.

Code 43 (Knock sensor) signal to the PCM has remained low for too long, or the system has failed a functional system test.

The Dk Blu wire from the knock sensor runs to terminal B15 on the engine control module.

Have you checked continuity on this circuit, or checked to see if it is grounded?

Roger

I have waited all day for a response...please refund my money as no response at this time.

Patti

Sorry, Just got to this page...kept checking my e-mail. Yes I would like to obtain a wiring diagram, and once again I am sorry. My email is [redacted] . I have 5 volts going to the knock sensor.

are you out there?

Sorry for the delay. Had to help my daughter and it couldn't wait.

I'll get that diagram to you.

Roger

I have emailed the diagram for your review.

Roger

Thank you Roger....I am again sorry for my rudness about my answer. We are reviewing the diagram...will get back to you I am sure with more questions.

Patti

Roger,

The diagram was our salvation....now more questions as predicited....you were correct the B15 conneciton is loose...when we shut the glove compartment it wiggles loose and kills the engine. Would this be a computer problem or can I just get the wire stabelized and be ok.

You should be able to correct the loose connection.

Has the B15 terminal backed out of the connector or is it a damaged terminal that needs replaced?

Wish I could see it...

Roger

I wish you could also. When I first looked after your suggestion, I had 14 volts, after messing with it, I am down to 13 volts, I can hear an arching sound then kills engine all together.

We purchased a new computer...still not working....still showing low voltage...wire movement is gone...unable to wiggle.....

I'm sending you a Technical Service Bulletin(TSB) to review. It may not apply but it made me think.

Do you still hear the arching sound and then the engine shuts down?

Roger

Roger,

The arching is gone, volt reading of 13, rpm dropping 50, then engine dies. Seems to be intermintent. Got the TSB (thank you), read it I am hoping this is not whats wrong. I already use the other filter. Could injectors or fuel pump be a factor in this condition.

Thanks, Patti

Have you tested fuel pressure? Sure, it could factor if flow is restricted, or low.

The 50 rpm drop and then stall sounds electrical...crankshaft sensor?

Will the engine run long enough to warm up? Any codes with the new computer?

Roger

We removed temperture sending unit to TPS and truck runs great.....cold 14 volts, 165 temp dropped to 13 volts. Taking truck for drive.....have not checked codes again. Will write back in a little bit.

I'll be out for a while..

Roger

How is it going? I have been out a lot as I have a very dear friend in the hospital.

Roger

Roger, Hope your friend is getting better. As you can see by my last response things are still not going well. No crank or cam sensor on truck, fuel pressure is good, disconneted the temp. sending unit for the tps, and truck will idle without dying...still has hesitation and lack of power. B15 terminal still low voltagewhen motor reaches 165 or close and still code 43. Knock sensor plugged in or not doesn't matter. Perhaps wire harness is Bad? Getting fustrated...its only a vehicle...should be able to fix....Thanks, Patti

My friend will not be getting much better for long. He is 82 and the end is nearing. Thank you for your kind words.

Have you ran a continuity test on the Dk Blu wire from the knock sensor to the B15 terminal of the computer with both components disconnected? While disconnected, have you checked this circuit for shorts to ground?

That would tell us if this circuit needs a replacement wire.

Roger

Roger,

With both ends disconnected ohms reading was 4.38 and with wire still disconnected checked the computer end and to ground...got .08 reading. I am assuming that the wire is grounded somewhere on the circuit. Can just the b-15 wire be replaced or do I need to purchase an entire wiring harness. Thanks, Patti

Wow, with both ends disconnected that reading does seem too high. Did the test leads from the meter make really good contact.

Yes, the B15 wire can be replaced alone. The wiring diagram does not show it spliced to anything else. Leave enough wire from the old harness exposed that reversal will be a possibility.

Route the new wire out of harms way. Let's count on a favorable result.

Roger

HI, Just an update...after replacing computer, wire harness, and all electronic parts...guess what...distributer cap was broke (yes the new one) oh well.

Thank you again for all of your help you were wonderful and I wish you well.

Thanks, Patti

What then shall be done with this question?

If you agree to accept my help as an answer so that All Parts will pay me please close the question or click on the OK TO PAY MECHANIC button.

Need something else? Please advise,

Roger

1995 GMC Sierra 1500 Extended Cab Pick-up Ignition System   

I have a 95 GMC with a 5 speed. I am having an recurring problem that baffles me. The truck will not start after it sits for a long period of time. It will turn over but it will not catch. I have good cranking from the battery and the fuel pump, filter are new within the last 6 months. If I push start the truck and bump start it fires right up and then normally I dont have a problem with it for the rest of the day. I can go out and turn the key and it will start right up. If I let the truck then set overnight it will not start then the next morning unless we go through the push and bump start process again.

Hi, Makes me think that there is a problem with the fuel rail pressuring up with just one cycle of the key.

What happens when you test fuel pressure with the first attempt to start the engine after overnight? Will the fuel rail hold pressure after the key is turned off?

Roger

I have not tried that I have no means to test fuel pressure. Do I need to take it to the local shop?

Without a means to test fuel pressure you will need some help. Be prepared to leave the truck long enough for the condition to be present. Then the problem can be identified.

One thing you might try is to turn the key to on but do not attempt to start the engine. Wait two or three seconds. Turn the key off. Repeat this two or three times. Then try to start the engine as you normally would.

The fuel pump should run for two seconds when the key is turned to on to pressure up the fuel rail for engine start and then stop. If it is quiet around the truck can you hear the fuel pump run for the two seconds when you turn the key to on? Sounds like a hum.....

Roger

The fuel pump runs as it should for about 2-3 seconds and then I dont here it. I asked a local mechanic where I live and he suggested the same thing I am going to have to leave it to try and diagnose the problem

You are on the right track to get this diagnosed properly.

It would be a huge benefit to you if you are present when the attempt to start the truck is done. You'll know first hand if the mechanic experienced what has been happening to you when you go to start the truck after it has set for a good while.

An honest mechanic is all you need for a fair deal. He will diagnose the problem, estimate the repair cost, ask for your authorization to proceed, and do only what is authorized.

If we are finished please click on OK to finish up. If not, please advise.

I thank you,

Roger

1994 GMC Sierra 1500 Extended Cab Pick-up Chassis / Suspension & Steering Malfunction When braking Always

Excessive pedal travel (almost to the floor) with little brake power. Claipers and pads are three months old. Replaced master cylinder, no difference. No leaks in system. Problem came about suddenly. Brake light does come on when pedal reaches the bottom, and stays on.

sounds like you may have a defective master cylinder (even new they can be bad).. or check behind the dust boots on the caliper pistons and rear wheel cylinders... otherwise you may need to have the system power bled to get any trapped air out.

I'll check those possibilities. Also, anything in the metering/combination valve that could allow the fluid to circulate?

metering valve usually wont make your pedal drop unless it is leaking ,and that you would see.

1993 GMC Sierra 1500 Extended Cab Pick-up Fuel System   

1993 k series 5.7 L truck starts every time but stalls after aprox 60 seconds and wont restart unless I leave it alone for an hour.

Hello, Have you checked the fuel pressure? Has the fuel filter clogged up? Do you know the maintenance history of the truck?

Roger

I changed fuel pump, fuel filter, IAC, fuel pump relay, map sensor,O2 sensor, EGR valve, fuel pres regulator, ECM and e-prom, ignition coil, and TBI injectors to no effect on the problem. Seems like it starts and runs but then gets a signal to shut down fuel. Sometimes the tach fluctuates wildly before it stalls.

With all of this done I'd want to test the pick up coil in the distributor.

Pick-up coil continuity is tested by connecting the ohmmeter (on low range) between the white and green leads. Normal resistance is between 500 and 1500 ohms. Move the vacuum advance arm while performing this test. This will detect any break in coil continuity. Such a condition can cause intermittent misfiring. Replace the pick-up coil if the reading is outside the specified limits.
If no defects have been found at this time, and you still have a problem, then the module will have to be checked. If you do not have access to a module tester, the only possible alternative is a substitution test. If the module fails the substitution test, replace it.

Roger

Roger thanks for the suggestion as soon as I get a chance I'll change the module, falls in line with my bouncing tach

Tim

Thanks for the update. Post again when you can.

Roger

1992 GMC Sierra 1500 Extended Cab Pick-up Engine Chugging When driving When warm 

When I lightly depress the accelerator such as in a parking lot to drive slowly or back of the accelarator slightly the engine will chug and hesitate almost like it is flodding or missing, like it has a performance cam. As soon as I depress it more and accelrate harder or completely back off it runs perfect. any suggestions. I have replaced the air filter and fuel filter last week. Did not help.

Do you have a tbi or multiport injection?

Any check engine light at anytime while the engine is running?

Check your throttle position sensor, it may have a glitch causing a faulty reading when the hesitation occurs.

It is a TBI. Where would the Position sensor be located and is there a voltage range or OHM reading range. Thanks!!!!!!!!!

It will be easiest to simply give you a link to a free online repair guide for your vehicle, there you'll find the location and testing procedure for the sensor - Copy and paste the following link into your address bar-

http://autozone.com/servlet/UiBroker?UseCase=RG001&UserAction=viewRepairGuideYMMEYear

Thanks Douglas,

One last question. I checked everything out last night with the TPS and the voltage range at different throttle settings is consistent and within range of what the book states, eliminating the TPS.
I did unplug the vacuum line off of the EGR valve and it ran perfect but pinged under load. I then re hooked and disconneted the line from the front side EGR solenoid valve and it was the same result. I am convinced it is either the EGR valve or solenoid, but snce it did the same thing (ran perfectly) when I disconnected the vacuum line before and after the solenoid to me it seems it would be the actual EGR valve. Any commnets- Thanks!

Okay, if you can operate the EGR valve by hand see if the spring is weak or not.

I can depress the plunger on the valve very easily by hand.

Okay, be sure to check the plunger resistance on the new one to be sure there is a discrepancy before you buy.

1992 GMC Sierra 1500 Extended Cab Pick-up Heating / Cooling System   

The airconditioner will not work, when the truck is started or when the A/C blue button is pushed the A/C sign flashes 120 times. There is no 12VDC to the clutch. I recovered the freon and serviced the system back to 2.5 lbs. I jumpered the clutch with 12VDC and the clutch engages and the system blows cold air. According to the crapy Haynes manual wiring diagram there is a A/C compressor clutch relay controled by the vehicle control module. I cant find either. I followed the clutch wires back to the fire wall, no opens in the wires. Where do I go next?

Hello, Did you find a low pressure/cycling switch on the accumulator? Knowing you have sufficient freon I wonder if this switch is bad. Try jumping the two wires on this switch. If the clutch engages the switch may be a bad one. It is not necessary to recover freon to change this one.

Roger

I jumpered the switch,to no avail, no power to the clutch, still...and as I was servicing the system I could hear the switch make, and I also check for continuity be for and after the service, I know the switch is working. Do you know what the A/C flashing 120 time means? and do you know where the clutch relay and control module is located?

The control module should be behind and above the glove box.

I haven't yet found the reason for the a/c flashing.

Have you looked on a bracket on the firewall for the relay?

I'm going to look for a wiring diagram for the wire colors on the relay.

Roger

What engine? Carb, or F/Injection?

Roger

its a 5.7 350 V8 with throttle body fuel injection

Do you find a letter size box lying flat on top of the left inner fender with three connectors plugged into it? It will be silver-gray in color and have metal rib cooling fins on it's top side.

If so, that box is the engine control module.

Roger

I will look, any progress on the flashing A/C (120 times) when the system is turned on or the truck started?

I will have access to a better data base tomorrow. I hope to get the answer there.

Roger

Okay, There is a Technical Service Bulletin (TSB) that says the A/C Control Head flashing is due to "Light surface corrosion on the control head terminals".

The A/C clutch relay is on top of the A/C plenum, behind the right side of the dash.

The Powertrain Control Module (PCM) is behind the right side of dash, above the blower motor.

Tell me your email address and I'll send you all I found in the Mitchell 1 Auto Repair Data Base.

Thanks,

Roger

my email is [redacted]
Thank you,

How well did the emailed documents answer your question?

Roger

I think the info you gave me is great, but I have not had time to do anything on the truck this week end yet, but I will let you know, Thanks again.
Wade

I cleaned the conector at the back of the control head, started the truck, no A/C flashing! I turned on the A/C and the compressor clutch engaged, its only 57 deg. outside so it cycled right away, but it apperes to be working. Thank you!

That is really good news. To accept my answer so that All Parts will pay me please close the question or click on the OK TO PAY MECHANIC button.

I thank you for your patience.

Roger

1992 GMC Sierra 1500 Extended Cab Pick-up Brake System   

The left front brake was not releasing completely. I bled the system. Problem remained. I replaced the front calipers and pads and bled the front brakes. The problem seems to be worse. ?????

Hi, I've seen this before! What is happening is the flex hose that connects the brake caliper to the system is collapsing inside the hose and restricts return flow to the master cylinder.

Replace both front brake flex hoses and re-bleed the front brakes. Start with the right side.

Roger

What is the status of this question please?

Roger

1991 GMC Sierra 1500 Extended Cab Pick-up Engine   

I recently had the engine in my Sierra rebuilt. When it was completed the shop manager informed me the "check engine" light is staying on. After more than a week of searching for the problem, he called to inform me that the ECM needed to be replaced. With uncertainty in his voice he attempted to 'consol' me that this is a common problem.
If this is a common problem, how common is it? And/Or, could this have been prevented, via a procedure perhaps the mechanic failed to follow?
Thanx, sincerely disgruntalled

Well, it begs the question: "Sir, is it common for you to need a week to find a "common" problem?" I certainly hope they are not trying to charge you a lot of labor to track down this problem (I'm sure a used ECM can be found for less than one hours labor-- vs dealer labor rates here).

Which engine size do you have?

What is their estimate for a new ECM? I think I'd opt out of having them replace it at this point UNLESS they guarantee it will fix the problem & have a reasonable price.

Did they say which trouble code is present (should be one stored in the ECM when the engine light comes on) ? If you have the truck now I can tell you how to retrieve the codes with a paper clip, simple to do.