OBS no DRL or fog lights

[Blueridgerunner]

I have a 99 Z71 Tahoe. DRL & fog lights don't work. Fuse#15 ok, Green light in dash comes on when it's supposed to. Tried to locate the relay but I can't find it, nor the module. Any idea where to look or troubleshooting suggestions? All other lights/functions working normally. I looked back thru old posts but having trouble finding any. Thanks

 

[SunlitComet]

relay is on convenience center. module is in a plastic case typically tapes to the biggest wire bundle near the parking brake. However ....

The fog and drl feeds split right off the fuse terminal so your problem might be the fuse block itself or further upstream. Do your courtesy light and parking lights still work?

 

[TheBlueBeast]

Sun -

I read somewhere that if the parking brake is on the DRL's won't work. I know the previous owner of my truck "fixed" the brake light by putting black tape over the dash light. I was told a stop light sensor would fix that for me. Haven't tried it yet though.

 

[LI99HOE]

Double check this as well.
The daytime running light diode is a common failure on these trucks. It is located under the drivers side of the dash.

The daytime running lamps (DRL) diode consists of a black aluminum case with fins. The diode attaches to the instrument panel (IP) harness behind the left side of the IP.

 

[SunlitComet]

Sun -

I read somewhere that if the parking brake is on the DRL's won't work. I know the previous owner of my truck "fixed" the brake light by putting black tape over the dash light. I was told a stop light sensor would fix that for me. Haven't tried it yet though.

if the parking brakes is depressed it will disable the drl yes. but his indicator light still functions which suggest the module is receiving its ignition sense and is reacting to it and that the parking brake disable circuit is not active. and a;so by taping it off you disable the same light that will tell you something is wrong with the brakes. SO TAKE THE TAPE OFF. A new brake pedal/stop light switch will not fix that. it is supposed to work that way.

---------- Post added at 12:47 PM ---------- Previous post was at 12:37 PM ----------

Double check this as well.
The daytime running light diode is a common failure on these trucks. It is located under the drivers side of the dash.

The daytime running lamps (DRL) diode consists of a black aluminum case with fins. The diode attaches to the instrument panel (IP) harness behind the left side of the IP.

The diode just prevents volts backtracking into other areas so if his drl AND fogs lights are out the diode should not be the issue. the only thing they have in common is that fuse on the block. However the headlamp switch needs to be on and in low beams for fogs to even function so if you turn on the headlights manually and the drl indicator is still lit something is wrong with the headlight switch or drl module. if the light goes out then most likely the drl relay.

 

[LI99HOE]

Only said it was a possibility Jonathan.....

.... and the diode works in conjunction with the DRL circuit board, so that when the diode is biased on the circuit is active. If the diode is open the DRL's won't function. I never said it would fix both problems at the same time, and am guessing he might possibly have 2 separate failures

 

[SunlitComet]

Have at it then.

 

[Blueridgerunner]

Thanks guys. The DRL indicator light goes out when the lights are turned on but still no DRLs light up. Parking lights and courtesy light work normally. DRL lights haven't worked since I acquired the truck. However, the fog lights worked until recently. It is possible that both fog lamps are burnt out so I will check. I did, however, replace them about a year ago. No power at lamps. Further checking

 

[Blueridgerunner]

Further testing reveals that I have 12V coming into the switch (grey wire) but nothing going to lights (purple wire). Switch seems to be made out of unobtanium. Any ideas about replacing it with an aftermarket switch?

 

[SunlitComet]

what switch?