2001 Tahoe Headlights stay on (Stuck)

[Thinkster]

My girlfriend was sitting in the Tahoe the other day at lunch for about 30 mins. with the ignition switch on so she could listen to the stereo. Little did she know that the headlights and taillights were all on even though the vehicle was not running. So when she went to leave at the end of the day, the vehicle would not start (as the headlights/stereo running for that time drained the battery).
So as far as I know, the Headlights should NOT come on with just the key in the ignition and the light selector switch in the 'Auto' position on a sunny day.
I pulled the Headlight relay out to test it with my meter and it is o.k.

I was thinking the ambient light sensor may be not working correctly, but wouldn't the vehicle have to be running for that to take effect?

Any ideas? I'm thinking bad light selector switch or bad ambient light sensor circuit or worst case scenario, bad BCM.

 

[Blazed]

My automatic headlights are on when the key is turned too. I think this is how they all are.

 

[JochenWoern]

My automatic headlights are on when the key is turned too. I think this is how they all are.

I as well think this to be the case.

Easy way to check. Have the girlfriend do what she did when the battery drained. Check if the lights stay on, then turn the headlight switch from AUTO to OFF. If the lights then turn off, I would imagine all to be wired correctly and in good shape.

 

[Thinkster]

I could understand the lights coming on when the vehicle is running as the alternator would be charging the battery, but for headlights and tail lights to come on when you have the ignition switch just to the on position so you can listen to the stereo without the vehicle running seems stupid as that would be a quick way to drain your battery!

 

[Screwd up 6]

I could understand the lights coming on when the vehicle is running as the alternator would be charging the battery, but for headlights and tail lights to come on when you have the ignition switch just to the on position so you can listen to the stereo without the vehicle running seems stupid as that would be a quick way to drain your battery!

Although it may be stupid, the lights are set to come on when the key is turned to "on". With the key set to this...everything is "on". The blower fan for the a/c and everything. If the sun is out, then headlights might not come on, but all accessories will be powered thus draining the battery fairly quick. When you are wanting to listen to the radio only, turn the key back to "acc" and this should only allow the radio to work.

 

[JochenWoern]

Although it may be stupid, the lights are set to come on when the key is turned to "on". With the key set to this...everything is "on". The blower fan for the a/c and everything. If the sun is out, then headlights might not come on, but all accessories will be powered thus draining the battery fairly quick. When you are wanting to listen to the radio only, turn the key back to "acc" and this should only allow the radio to work.

^ +1

 

[Thinkster]

I can understand DRL lights coming on, but it still doesn't seem right to me for headlights to come on in bright sunlight just by turning the ignition switch to the ON position. I know the ignition switch provides power to various things when it is in that position, but there should be some logic to say "Hey the car is not started or running and it's sunlight outside, no need to turn on headlights and waste the battery"
From what I gather, that's the BCM's job, so if it controls the headlights then maybe the photocell is bad or not being read properly. Anyone have a pinout for the BCM?

 

[kschumake83]

Press the e brake down before you turn the key on, problem solved. But to find more about the other problem if the engine is running do the daytime running lights work or does it go straight to the headlights?

 

[Thinkster]

So are you saying the e-brake may have something to do with it? She doesn't use the e-brake as the cable assy. on the e-brake broke some time ago. so if she engages the brake, she would need pliers to release it.

 

[KR66]

My girlfriend was sitting in the Tahoe the other day at lunch for about 30 mins. with the ignition switch on so she could listen to the stereo. Little did she know that the headlights and taillights were all on even though the vehicle was not running. So when she went to leave at the end of the day, the vehicle would not start (as the headlights/stereo running for that time drained the battery).
So as far as I know, the Headlights should NOT come on with just the key in the ignition and the light selector switch in the 'Auto' position on a sunny day.
I pulled the Headlight relay out to test it with my meter and it is o.k.

I was thinking the ambient light sensor may be not working correctly, but wouldn't the vehicle have to be running for that to take effect?

Any ideas? I'm thinking bad light selector switch or bad ambient light sensor circuit or worst case scenario, bad BCM.[/Qthinking

I just had This same ISSUE and could not find the answer anywhere I solved it! Turns out the Ambient Light Sensor went bad! It's on the dash between the defroster vents a little black thing sticking up! They go bad from time to time from having the sun beat on them day in day out! It's a $15 dealership part yes $15! I spent 2 weeks searching the net for a answer and found nothing reliable or even remotely relevant to the issue! If this part goes bad the vehicle will think it's night all the time and turn on the headlights whenever the key is on and the parking brake is off!!! Save yourself a bunch of money and try this part first it's so simple and common it's stupid! With all the answers I got about (it happening with there Ford guys this is a GM different system all together) that wasn't here but it doesn't help when people start making suggestions to disable This cut that and just bypass the issue (DON'T DESTROY YOUR VEHICLE) because someone that had no idea what they were doing told you how they fixed there vehicle.