Envoy head lights

gmc
envoy

#1

low beams / running lights are out. voltage is 11.5 at light plug, and i changed the bulbs (did not touch them). i’m an electrician who knows nothing about cars, so needless to say i’m stumped. thanks for any input.


#2

I could be incorrect, but I’m guessing that the current runs from the fuse to the light to the relay contacts to the stalk on the steering column. I assume you measured to voltage from the connector pin to ground? Try grounding the “ground” side of the connector with voltage to the bulb. If the bulb lights, then I’m probably right and a schematic would be a good idea. A Haynes manual from the parts store would have that schematic in it.

Actually, get the manual anyway.

Post back.


#3

that is a good idea. i’ll give it a shot tonight and let you know.
thanks and wish me luck.


#4

The Trailblazer and Envoy are first cousins. You don’t state the year of your 'Voy. My 2004 TB schematic shows that both low beams are fed from the Headlamp Driver Module (HDM) which is relay 46 in the engine bay fuse block. That relay is controlled by the Body Control Module (BCM) which is under the back seat in the rear fuse block.

Strangely enough, the schematic shows an A and a B wire for the Hi and Low beams respectively but not a ground wire. If you measured close to 12V on one wire to bare metal chassis ground, check the lamp ground wire to bare metal chassis ground. If it also reads 12V, you have a bad ground.


#5

mine is an 04 also, and that is just the info i needed. i’ll check it out tomorrow and let you know how it turns out. thanks


#6

finally found out what it was. the connectors that the bulbs plug into were bad, which caused the relay to blow. they looked fine and showed no signs of damage, but the gm guy said that he had ordered several of them over the past few years so it must be a glitch. $190 later (2 relays, 2 connectors, 2 bulbs) and the problem is solved. thanks for your input.