I've had an issue with my '06 TL since buying it where locking and unlocking the doors with the key fob resulted in only the passenger front and passenger rear doors locking/unlocking, and the driver front and driver rear doors did nothing.

I, like many before me, immediately assumed it was door lock actuators, and I set about replacing them. The driver front door now locks and unlocks with the rest of them but the driver rear door does not.

So to reiterate, even after replacing the door lock actuator, the driver's side rear door still does not lock or unlock with the key, and the lights do not flash like they should when locking the car, and the security light does not illuminate.

Then I tried to bench test my door lock actuators to see if I ended up getting a bad replacement unit, and by applying 12V to the smaller of the two connectors, both my original unit and the replacement unit seem to be functioning.

I tried using my multimeter to get a reading from the harness to see if the actuator is getting power and its hard to tell, it seems to cause voltage spikes when pressing the unlock button but not the lock button, however the actuator does not exhibit this behavior, it doesn't lock or unlock when plugged in.

This really has me scratching my head, I've checked all the fuses (all fuses, not just ones I deemed related to the door locks) and they all appear fine, I checked for settings in the MID and nothing seems to be the issue there, my last guess is a bad ground or a split wire somewhere, but before I go digging through the harness like a madman I figured I'd ask here in case someone else has had this problem.

I've searched far and wide on these forums and everyone else's issues seemed to be resolved with replacing the offending actuator, or having bad door or hood switches, neither of which seem to apply to me

Thanks in advance!

 

A test light might be helpful in diagnosing this problem. If you work at night its extra easy to see when you get power. I would suspect a loose wire somewhere or a bad ground. Some continuity testing would also be good to do. YouTube is your friend.