Hi fountains of all knowledge.

I’ve recently bought a 2013 q5 50tdi and realised the neither back doors lock or unlock using the fob.

They can be locked by turning the white screw on the door edge and unlocked by pulling the leaver.

VCDS pointed to faulty CCM have changed that at great expense and the fault remains.

I’ve checked the wiring and all seems well until you actuate the fob and the back doors voltage never changes. Like it’s not getting a signal.

It could just be the lock modules I guess. Wouldn’t vcds point this out though?

Any thoughts or even better known solutions are greatly appreciated

Cheers

Anthony.

The usual cause of this problem is damaged wiring in the corrugated rubber tube between door and frame. The insulation cracks as a result of the repeated flexing, leading to shorts and/or fracture. It would be worth peeling the rubber back to reveal what lies within as a first step.

Thanks cliff. Already done and no signs of breaks or cracks. And as in my post I have correct voltage at the plug. Accept no voltage change when asking for lock /unlock on the fob as you’d expect there to be.

3 hours ago, 30boz said:

Already done and no signs of breaks or cracks.

Including the driver's door?

Haven’t looked at the drivers door. But it and the front passenger door work fine.

The driver's door lock is the master that controls the other doors.

Thanks for the info cliff. I’ll be pulling the wiring boot and the door card off. As I’m getting some volts to the back doors I’m looking for cracked sheathing on a wire rather than a break ? Is there a way to test the wire out ?

I believe visual inspection is the best test. While a completely broken wire can be found with a continuity test, the damage can be as slight as cracked insulation that only shorts out as the wire chafes against metal during door opening.

Any progress on this Anthony?

Nope. No joy. Can’t find a broken wire. The boot lid doesn’t open or close properly either. The open does a few inches and stop. The close doesn’t work at all. It was intermittent and now it’s all the time. Any chance that’s related to the back doors ?

Having eliminated the most likely fault it's time to look elsewhere. If the fault is affecting both rear doors and the boot I doubt all three individual locks are defective, so it must be a control problem, though I would expect VCDS to have revealed it. All I can suggest is an auto electrician.

VCDS says ccm fault. I started by replacing that and it changed nothing 🤯

It’s been to an auto lec as well spent a day on it and found no fault either. 🤯

That’s what bought me here. Someone somewheres seen this fault before. It can’t only be my car.

Cheers for your input tho.

I have a feeling that the CCM may need to be coded to the car. Not entirely sure though.

Is rare as it sounds I had two rear lock units fail at the same time on a A4.

For the sake for a pattern part what's the harm replacing one for peace of mind .

Did they need coding in ? I’ve bought one to try it. Seeing as everything more logical checks out it could be the locks!

I can’t code to the car though.

Cheers

No coding needed. Just have to clear all alarms via auto scan