Hey guys, i got a 2000 Sunfire GT in November, and have been running the fog lights since I got the car. The person before me didn't use them. Up until a week or two ago, they were working fine. Hit the switch, green LED and fog lights come on. Hit it again, they go off.

Now, when you press the button you don't get the light, or the fog lights. I checked the switch and when I press the button, it completes a circuit between the orange and purple wires. When not pressing it, you get 12v across the purple and black wires.

Thinking it might be the switch, I put a jumper wire across purple and orange, and got nothing.

I then checked the relay, which gets 3v on the orange wires (pin 30 and 85 or 86) across the green/white wire (again 85 or 86, can't remember which one was ground, and which was 12v). Hit the switch, no change.

I then applied a 12v current to the orange wire coming from the switch, and get no change at the relay.

Next I applied 12v to pin 87 on the relay connector (with the relay unplugged) and I get fog lights. Apply 12v to engage the relay, and the relay works.


1) Is the switch momentary contact? or is it a push on push off switch?
2) I assume I must have a wire problem, which is why only 3v shows at the relay
3) Can I just run a new wire from the pin on the switch which corresponds to the orange wire, and run it to the relay? Or does the switch run through the BCM first, which tells the relay to activate?

If it is a wire issue, I'm thinking of changing the whole setup so that the fog lights are my DRL's, bypass the factory DRL system (via the BCM hack: cut wire B4, on connector C2, and ground). My only issue is the fog lights will then be on all the time, even if the high beams are on, which is not completely desirable for me... However, I could always put another relay in, which when activated by the high beams turns on, and as a result cuts the power to the fog lights.

But really, I am just looking for a way to get my fog lights working as they were before right now. Too cold out to do any real wiring projects

Alright, after taking the switch apart, I've found that it's definitely a momentary contact switch. So I'm guessing it must run through the BCM.

Sadly my Haynes manual was purchased in 1998 when I got my original Sunfire. So I have no idea how the 2000+ fog light system works.

If someone could post (or mail me) a wiring diagram for the 2000+ fog light system, I'd be very appreciative.




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"Humpty Dumpty sat on a wall..... Nobody knew what he was doing up there anyway"

In the interest of saving people time, and more knowledge being available.. Here's my solution I finally came up with on my own, and how.


After my initial diagnosis, I ripped out both the headlights again, took the intake resonator and washer fluid tank out. I then removed the battery, the air filter housing assembly, and the fuse block (the one under the hood). With these out of the way I was able to finally start chasing wires. Foolishly, I started with the switch again. Moved down the line to the BCM, and still everything tested ok.

Next I went to the relay, and started to remove all the wire loom and electrical tape moving outwards from the relay, towards the fog lights. I then proceeded to uncover the wiring all the way to the harness' connector in the engine bay (the one that sits in between the battery and transmission area). (Large black connector)

With everything I could think of exposed, I started to check for cracks or cuts in the wire, moving from the large connector to the fog lights. In the area of the washer fluid tank, I found a splice that was corroded through (three wires taped together with black duct tape). Repair that splice and move onwards. Getting closer to the relay I found another splice corroded, and fixed that (orange wires - 12v supply). Moving towards the passenger side of the car, I found yet another splice that was corroded. Repaired this splice as well.

At this point, I put some stuff back together, reconnected Connector #2 onto the BCM, fired up the headlights, and hit the fog light switch. Great success!


Overall procedure: 7/10 on the annoyance scale. Start by taking the relay apart and sending power to the fog lights. If they work, test the switch. You need to have a multi-meter to check the resistance on the switch so you can tell if it works (should be a closed circuit across the outside pins when you have the switch engaged). Next check the relay to make sure it functions properly - apply 12v and ground to activate the relay - if it clicks, then check the resistance across pins 30 and 87 (if it's closed, the relay works). Finally, if your switch is good, and your relay is good, start peeling off the electrical tape and wire loom. You should have the headlight out already by this point. Removing the washer tank is not a necessity, but makes it easier to access the wiring near it. Look for rust first, and fix any areas where you see rust coming through the tape.


I hope this saves someone hours of time which I wasted by checking unnecessary things, and removing parts that don't need to be.

i have the same problem with my 04 sunfire currently, and i will be trying this nice work

My '00 cav had the headlights go out at night. My brother came and put a jumper so I could get home. We found the connector for the lights had rested on the transaxle housing for 4 years since I got the car and the heat had melted through the housing. Water got in there and fried the circuit. He cut off the connector and reattached each wire with solder and heatshrinked the repairs. I wonder how many other cav's have been victims of GM's design. Should have had a bracket in the design.


"...smells like cheese..."-Stewie Griffin

00+ the BCM controled the foglights. the switch just sends a pulse to the bcm to turn them on