Headlight problem, need help
 

I was parked at the ATM tonight and my headlights started going off and then back on continuously. The switch is always on the off position because the lights obviously come on when you start the car. Luckily I switched the light switch to headlights on and they stayed on the whole way home. Anyone have this problem and how do I fix it? Any help is greatly appreciated.

Alright, you override the Twilight Sentinel and the headlights remain on steady. Just for the heck of it, try this out. While it is day light, ignition on, headlight switch off, place a dark colored piece of material over the ambient light sensor (dome in center) on dash. Check to see after a short time delay that the headlights come on and remain on steady.

I'm in agreement with Mark...possibly a bad sensor or bad connection at the sensor.

How brightly lit was the ATM area? Did your lights cycle on and off quickly, or was there a delay? Any flickering lights in the ATM area? I'd go with Mark's test, also. There is a delay built in so that short term lighting changes don't cause problems like that. If Mark's test works out okay, and it works fine away from that area, you may have just run into one of those rare cases where the type of lighting caused the sensor to go bonkers.

in a partially lit parking lot i could definately see that the light hitting the sensor is just on the edge of auto turn-on, and could very possibly cycle every 5-10 seconds (whatever the delay is in the car)

When I got home it was still doing it so it wasn't the lighting at the ATM, but I'm gonna try what you guys suggested and see what happens. Thanks for the help and quick replies.

I used to get that when I would pull up to my old roommates garage to put my car away. I'd pull up, park, get out and open the garage door, and sometimes my headlights would flicker like you're describing, without much delay at all. Almost like it was enough light reflecting back to trick the car. When I put the car back in drive the lights would come back on and stay on, it would only happen in park. This also happened once at a gas station that I was idling in park while a friend ran inside.

It hasn't happened in a good long time now, but it almost seems that the sensor is more sensitive when in park...? Since I never had a problem when I put the car back in gear.

Actually it does only do this while in park. How do I go about fixing this and how much does it cost?

My problems just disappeared after a few weeks of it doing this. I haven't had a problem since. I still don't know what was causing it. I assume something going wrong with the sensor itself. Hopefully yours fixes itself too...

I am not sure if this is the same thing or not, but I have this problem sometimes when I do not disarm my alarm properly. I have an automatic starter in my car, so I'm not sure if the wiring of the auto starter may have caused this, the auto starter's alarm remote may not be as good as the OEM, or who knows.

All I do know is that I have had this happen to me a few times, and usually hitting the unlock button on the remote again will disarm the system and the lights stop flashing.

It hasn't happened to me in a while, soooo...that's why I am a little vague on what exactly caused it.

That sounds weird, but i'll give it a try. Thanks for the tip.

I would suggest getting it checked for codes. Mine has the same problem and it is either the Fog lamp switch or the CCM (climate control module)/ this is your a/c control head. I'm going to check mine here in the next week or so. Let me know if you can get it check for codes and what the codes are. I could post up the diag. flow charts for the codes so you could fix it.

Will a light issue on an 00+ pop a code?

Yes it will. It's not stored in the pcm. I may have misinformed you on where the code may be set if it is th fog light switch or DIM like mine is. It will be in the DIM-Dash Intergration Module,IPM-Insturment Panel Module this is not you insturment cluster. Both of the module are considered a body control module of some sort by GM.

Edit: if it is a twilight sensor the code will probably be stored in the CCM as stated above.

How can these codes be retrieved?

I don't know if any aftermarket scan tools can read Body Control system codes. I have access to a GM Tech 2. That is how I retrieved my codes.

Good info...learning more everyday...thanks

I have had the same thing happen to me but I have decided that it is just some wierd cut-off point for the twilight sentinel. Like the posts previously, it happens only in Park and in situations where there is a questionable amount of light/dark. Mine does it in the garage sometimes depending on how much morning sunshine there is and it also does it at drive-thrus (especially Taco Bell) when I have to put it in park because they are taking too long. I don't see it as too much of a problem since I by-passed my DRL's the first week of owning mine. I wouldn't worry too much, but that's just me.

GO IRISH!!
PASS RIGHT

Agreed it will not cause any problems or turn on any tell tell lights. The system is overrided by placing the vehicle in gear or turning the headlights on with the switch.

Yeah, exactly. When mine would do it, I'd just turn the headlights on manually - until I put the car back in gear. Not a big deal.

The Tech II scan tool is connected, and is used to communicate (via Data Link Communications) DLC with the various control modules such as the DIM, IPC, IPM, DDCM, CCM, RIM etc.