QuestionI have a 2000 gmc yukon xl 4x4, my fog lamps will not turn on. The orange small light inside the cab dosent even light up. I changed the bulbs and checked fuses and relays, i even bought a new swith. Still nothing.
AnswerHi
Of course the fog lamps ONLY work with the headlamp switch ON, I am sure you tried this, correct?
If not, give that a try. Here is the circuit description:
The fog lights are controlled by the body control module (BCM) via the fog LP relay when the headlamp and panel dimmer switch is the head or park position.
The relay coil is powered by the output of the park lamp relay. The contact of the relay are hot at all times and is powered by the FOG LPS fuse. The BCM turns the fog lights on based on the input of the fog lamp switch on CKT 192 and the park lights on. With switch closed, grounding CKT 192, the BCM will supply a ground on CKT 1317, energizing the fog lamp relay. The fog lights receive current on circuit 34 and ground is supplied on CKT 150 to G100.
Some circuits are monitored by the BCM, and upon failure may set a DTC.
Check the purple wire going to fog switch WITH headlamps on.
It should be hot, if not fuse or relay OR RELAY COTROL which is the BCM (body control module).
If so the orange wire should be hot out of switch. This is the "request" for fog lamps to BCM. It should be hot at BCM connector B5 terminal C3.
Check grounds G100 ( on the DRIVERS SIDE radiator support) and G 203 ( Under the DRIVERS side A Pillar)
If all checks out OK, You MAY have a faulty BCM.
Follow post back if needed.
Good Luck
Pawl
