P0622 Ford - focus battery light

Question

I have a ford focus diesel, I recently fitted a new stereo and as I'd had the ignition on and off a few times I'd drained the battery :( so I bumped the car off and took it for a drive to try charge the battery up to no avail. Next I got the battery trickle charged and car and everything worked fine, until the next morning when the car was flat. I had a vehicle electrician check my alternator to find it was charging between 11v-12v. So I bought a new alternator from euro car parts. Fitted it myself as well as recharging the battery again. Car started fine all was well till I was on my way home from work(where I fitted the alternator) and the battery light came on, my first thought was should of put a new belt on but when I pulled over and checked everything was fine. Alternator was still charging as it should 13.8-14.5V so I turned the car off and started it up fine. The battery light was also off again until I turned the heated screens on and on it went again. I've checked the voltage on the smart charge pin 3 and it is reading the same as the battery with ignition on. I've also tried tracing the wires from the alternator back to the engine looking for a short but can only see so far. I've been having to take the battery off overnight to stop it draining. I have a friend who has a ECU fault diagnostic machine and it was coming up with the p0622 fault code. What else can I try before trying an ECM ?

Answer 1

the stereo wiring might be wrong, I would remove the stereo.