Alfa 159 Rear Doors Failing to Lock
A tip for anyone having this problem. If you haven't done so already, re-setting the body computer can clear up the problem of the remote not locking the rear doors. For me, it also cleared up the additional problems of the electric rear windows and the passenger doors unlocking button on the centre console not working.
This is free advice I obtained from a friend who contacted someone in the motor trade for advice. You should remember I am a total amateur and take no responsibility for your outcomes! However, this guidance saved me a lot of trouble and expense and thought it might be worth sharing.
The body computer can be found under the rear seat. The rear bench seat can be lifted by gripping it at the bottom (front and middle) and pulling it up sharply. You are looking for a black plastic box with cables connected to it. On my 159 it is located on the off-side (right-hand side) of the vehicle.
1. With no key in the ignition, disconnect the cable connectors from the body computer. Mine had two cable connections. Each could be removed after sliding back a purple (mauve?) plastic locking mechanism. One was blocked by the cable to the other connection but this was solved by removing the other connection first. Make sure the disconnected cables cannot short.
2. Start the engine and let it run for a few minutes.
3. Switch off the engine, remove the key fob, do not activate any locking and leave car "off" for 30 minutes.
4. Re-connect the body computer
5. Start the engine and run for a couple of minutes
6. Test rear electric window operation, passenger door unlocking button on central console.
7. Switch off car, remove key fob, exit car, close doors and test remote locking.
I should also mention that there is a fuse for the body computer - see the operating manual. I had already checked this before trying anything else. If re-setting the computer doesn't solve the problem, I'm afraid I can only suggest you visit a good Alfa repair business!