Audi Q7 4M - 2016 - Locking Mechanism randomly not engaging

[CiprianSS]

Hi,

Audi Q7 4M - 3.0TDI - 2016 UK
No Soft Close

Summary of the issue:

-I had a battery change at Halfords after a winter in which my battery has struggled
-After a week or two, we've noticed that the doors remained unlocked after we press lock button on the fob
-The alarm is engaged and the mirrors are folding, the fuel flap lock seems to get engaged as the mechanical sound of the lock itself is audible
-Locking with the fob blade is working, but only for driver door. Other doors remains unlocked.
-We don't know if that has happened prior to the battery change, it might be a coincidence
-The issue appeared randomly and I couldn't narrow what are the factors that might influence it
-I've had my vehicle to Audi on another issue, Front Camera is dead, but on the same visit I've told them to check the locking mechanism
-They couldn't replicate the issue
-I've took the vehicle home and the Locking issue has become more persistent than before
-I've changed the Fob batteries, but no success, the issue is still present and random
-I can replicate the issue now with an 80% success rate. I noticed that the issue tends to appear after 10minutes Drives or longer.
-After i get out of the vehicle and press lock button on the fob the locking mechanism is unresponsive, alarm is activated and mirrors are folding as before. But there is no mechanical sound of the Locks actually engaging
-I've also tried from inside the vehicle, using the button on the door, issue is still present, no engage from the Driver Door lock button and the "locking light" is not turning on
-If I leave the car like that and return in random amount of minutes, sometimes 1-2minutes and try to lock it from the fob, it works and the locks are engaging on all doors.
-Coming back to mentioning the battery change, I decided to have a look if Halfords actually coded my vehicle, I was thinking maybe there is a voltage issue within the lock itself. I've checked and seems like Halfords didn't code my battery as they said.
-I've tried after re-coding my battery, but the issue is still present. Same random onsets and random working periods.


1. I've got a video on how it's not locking.
WhatsApp Video 2025-03-20 at 21.49.25_3bb0f65c.mp4 - Google Drive

2. A video with the doors locking and the "mechanical sound" of the locks.
WhatsApp Video 2025-03-20 at 22.03.43_5a2636c0.mp4 - Google Drive

[Crasher]

What is the VIN? The problem will be stored in the convenience system memory so get a VCDS fault code scan done by a VAG specialist who cares rather than a main dealer who couldn't give a ****. I can't see it being related to the battery change or coding issue.

[CiprianSS]

VIN: WAUZZZ4M5HD010846

I've got a TOPDON ArtiDiag800 BT 2.

I've ran a complete check, there are multiple electrical faults, one was related to Central Locking...
I hope that Halfords ******** did not reversed polarity or disconnected positive first...

I did a clear DTC, central locking did not appeared any more and today it locked at first try...Hopefully is not just randomly working.

I still have some remaining faults (see pictures)
I do have a Ghost Immobiliser fitted last year, but with no issues until the battery change

I do have Audi Comprehensive extended warranty on the vehicle, but I feel like Listers guys are just not giving a ****.

IMG_20250320_203059.jpg - Google Drive
IMG_20250320_203055.jpg - Google Drive
IMG_20250320_203051.jpg - Google Drive

[CiprianSS]

You were right, the issue is still present.
Seems like the battery coding was not the issue.

I don't get what could be the cause for the mechanical locks not to engage, for a short period of time.
I went to a shop today and when i've arrived the locks were not working and after 5minutes in the shop the locks were working.

[Crasher]

The complexity of the 4M electronics cannot be underestimated, faults can drive a seasoned tech with the dealer system ODIS, to distraction.