[Chris Lowe]

I’ve spent hours searching through previous posts dealing with the ubiquitous door lock actuator issue without finding mention of this, so I’m asking for

The Short Version – I’ve replaced both rear door lock actuators on my 2007 335i sedan. Neither will respond to a lock/unlock command from the car. No noise, no movement. If I unplug the wiring harness from one of the new actuators and plug it into the old unit from that side, the old unit does work (it will lock, but just makes a noise when trying to unlock, so it has a mechanical problem). I can’t understand why the new actuators fail to operate.

The Long Version – I’ve had the misfortune of having all four door lock actuators gradually fail over the last six months. I became fairly adept at contorting myself to swap out the fuse which solved the issue early on, but eventually it became necessary to replace the actuators. Thanks to the contributors to the useful DIY replacement guides on this site, I’ve replaced both of the front door actuators and they are functioning normally. The rears are simpler to replace since they slide past the window mechanism without needing to move it (and without any swearing or skinned knuckles). The left rear didn’t function after installation, so I went ahead and did the right rear thinking that it would work and prove that the other was defective. Instead, neither of the rear actuators respond to lock/unlock commands from the car. They don’t make any movement and there is no perceptible noise. As I mentioned above, the old left rear unit functions as before if I connect the wiring harness up to it instead (I didn’t try the right). I have:
- Checked all the fuses associated with the door locks (but the old unit wouldn’t have operated if a fuse was the problem);
- Left the negative battery cable disconnected overnight in hopes that it would reset itself;
- Started and stopped the engine 5 times, trying the door lock button each time.
- Drove for an hour or so, stopping and starting the engine a few times during that trip.
- Changed the configuration of the door locking (“driver’s door only” to “all doors” and back again).

So, my conclusions are that either:
- The two actuators are non-functional (even though they didn’t come from a BMW dealer they do appear to be genuine products since the packaging and labeling is similar to the units that I got from the dealer for the front doors (the inexpensive kit that contains both actuators)), or;
- There is something else within the control system of the car that knows that a newer version of lock actuator has been installed and something needs to be reset to tell the car to work with it. Just guessing here. Certainly the replacements have differences from the originals (which is to be hoped!). I didn’t have this issue with the front door actuators, though. Or;
- These parts aren’t applicable to my vehicle (BM51-22-7-202-147, BM51-22-7-202-148). They are the part numbers that the BMW dealer said they were going to use when I asked them for the cost to do the replacements.

I did do the replacements without disconnecting the battery, but I think that is how most people on this forum have done it. I’m doubtful that would damage the actuators, but….

I’m stumped and would really appreciate any suggestions.

Thanks,
Chris

[BashShah]

hmm...
after actuator Install, try disconnecting negative Battery Terminal for 10-15 Sec and try again.
Basically a Logic reset I saw in a video sometime ago.

[Chris Lowe]

Thanks for the input, Bash. I have done that several times while trying to diagnose this, in addition to leaving it disconnected overnight. The actuators still behave as though they’re electrically dead, which I hope is not the case.

Chris

[BashShah]

I think it's dealer time.
Ohh and take your working locks with you.
Talk to shop foreman before hand and advise what you have done already.

Ohh you are in BC.
Where abouts? Have diagnosed with a BMW tool for codes?

[Chris Lowe]

My closest dealer is in Victoria, Bash. I’ve toyed with the idea of getting the least expensive Bavarian Technic setup, but their support people couldn’t say whether there might be some code related to this issue that their software would be able to reset. If all else fails I’ll ask the dealer to diagnose what the problem is. Hopefully this won’t end up costing me more than if I’d just had the dealer do the replacement in the first place!

Thanks,
Chris

[BashShah]

Do you have a K+D Can cable?
If so, load BMW standard tools on a laptop.
This will get you INPA for diagnosing.

[Kodak]

I had this problem recently, I searched this forum where it stated to check the fuse # 56 & 57 for my 2006, E90, and sure enough that was the problem and not the door actuator and to change the 15amp fuse to a 20 amp fuse.