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Audi A4 B7/B8: Door Lock Problems Diagnostic Guide

It can be an incredible headache to have to deal with issues related to the locking mechanism in your Audi A4. Read on to learn about some of the more common problems.

By Jeffrey Bausch - April 7, 2016

This article applies to the Audi A4 B7/B8 (2005-2015).

Are you having problems locking and unlocking the doors of your Audi A4? There are plenty of reasons why the mechanism might not be working. Fortunately for you, it’s something several other A4 owners have experienced. We’ve compiled some of the more common diagnoses they’ve come up with to help you troubleshoot and fix the problem.

Audi A4 Door Lock Problems Diagnostic infographic

Step 1 – Check if the child safety lock is engaged

If only the rear doors are experiencing issues, then this is an easy enough fix – simply open the back door and you’ll see that right there on the edge is a little black plastic keyhole with an image of a child on it. Simply turn it the opposite way it’s currently positioned, close the door, and test it out.

Child safety lock location.
Figure 1. Child safety lock location.

Step 2 – Test the key fob

Check the battery of the fob – try to lock and unlock the door from varying distances. If you notice that, despite being not terribly far away from the car, it is not reacting to the queue to lock/unlock the vehicle, then it might be time to replace the fob battery.

If the battery is not the problem, then you may want to try re-synching the fob to the car. Every fob has a different re-synching method, so research your fob’s owner’s manual to determine its re-synching process.

Check that the key fob is functioning.
Figure 2. Check that the key fob is functioning.

Step 3 – Check the fuse

All of the door locks are generally located on one fuse, so this is only a step to take if ALL of the locks are not working. If the fuse is burned, replace it.

Check for bad fuses.
Figure 3. Check for bad fuses.

Step 4 – Check the vacuum pump

The vacuum pump controls the locking system. Located inside the convenience control module, the fins on the vacuum pump are prone to breaking off. If and when this happens, the vacuum can no longer do its job, and the car fails to unlock when prompted. The only fix is to replace the module — go with used as opposed to new, as the latter is incredibly expensive, especially for such a minor issue.

Door lock vacuum pump.
Figure 4. Door lock vacuum pump.

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