GMC Yukon XL

2001 GMC Yukon XL Electrical / Lighting Systems  When driving Always

With headlights off - I select the left turn signal, the clock light blinks with the signal. With headlights on - I select the left turn signal, the indicator light is steady, buzzer sounds, inside lights blink in unison as though turn signal was working. Outside turnlights stay on steady and do not turn off until engine is off. This also happens with car in idle

These need to be diagnosed with a scan tool to access data from the bcm.

1997 GMC Yukon XL All Part Groups   

1997 gmc yukon 4x4 with vortec. Raw gas fumes coming from exhaust, running rough fowling the plugs, when trying to crank it all the guages jumping around on the dash, blinking check engine light when it is idling it is trying to run hot but doesn't. changed the plugs and wires already but made no difference. whats wrong & how do i fix it??? thanks :)

First you have to check for codes, why is the check engine light flashing?
Ensure the battery is fully charged.
If you do not get it scanned for codes and were just guessing, a good place to start will be the O2 sensor