Auto Electronics: Electrical, olds alero, body control module

Question
Hi Antonio - my daughter has a 2000 Olds Alero 6 cylinder.  Her interior lights will not always turn off when she turns the car off.  Other times she turns off the car and locks it and the lights go off and 5 minutes later the interior lights come back on.  They will only turn off when she unlocks the car and shuts one of the doors and re-locks her car.  Also, while driving the door locks lock and unlock unexpectedly. It seems to occur more often when accelerating.  I have replaced the body control module and ignition switch.  Any other ideas?  The car was in a minor accident where she was hit in the rear passenger door and this is about the time these things started to happen.  The rear passenger side door was replaced by ABRA.  After it was repaired and behaved as described above I took it back to the mechanic to check for a pinched wire and he did not find one or see anything out of place.  Appreciate any ideas on solving this issue.

Thanks for your help!

Mike

Answer
Hello Mike,

This type of vehicle, as with many others, has vehicle door sense switches in the door cavities.  Considering that the vehicle was in an accident it is quite possible that one of the sensors got damaged internally or a wire connected to it was damaged internally.  I would check them to ensure proper function.  

The door sense triggers control the signal that goes to the BCM (Body Control Module) which tells the computer that the door is either open or closed thus allowing the vehicle to lock the doors as it normally would when they are closed and the vehicle transmission is engaged.  

If one is damaged, it will send a bad or mixed signal making the BCM think the door is open when in fact it is closed, thus creating the lock/unlock problem you experience when driving.  

The fact that it happens more when accelerating makes sense also, given that when the vehicle accelerates, it moves at a higher rate of speed.  When this occurs the vehicle hits bumps in the road and/or experiences vibrations at a much greater force then it would when it is going slower.  Thus, if the door sense trigger is damaged or has a loose wire, a more forceful vibration or bump, as is experienced when the vehicle is going faster, would be more likely to cause the door sense trigger to send a false signal due to the excessive vibrations the vehicle is experiencing.

Also,  It is possible that there is a bad connection or ground wire at the control unit inside one of the doors, so I would check all the connections and wires behind the door panels.

REMEMBER the door sense trigger tells the BCM when the doors are closed, this information also tells the BCM to turn off the interior light, because if a door is open the light will either turn on or remain on, which is its job as it is a courtesy light.  This would explain your interior light issue.

It is very easy to miss the need for replacing a door sensor after the vehicle has been in an accident because many times the sensor will appear intact from the outside physical appearance of the unit, however, that does not mean there is not an internal or electrical problem hidden within or behind the sensor.

Start there and keep me informed of your progress, and if necessary we will go further into the diagnostic process.  But I think that most likely you will find that your problem lies somewhere within those areas I explained above.

Good Luck.

Thank you.