2012 Ford Focus mk3 1.6 battery light & alternator fault fixed! U012D U0284 P165B ford smart charge

Didn’t realise how often I say ‘erm’ until I rewatched this, really need to change that to ‘mmm-k’ to add to the comedic value.

Any who...

This Focus had a battery light on, it’d come on after about a minute of the engine being started and then would stay illuminated. The charging voltage was checked at the battery and the alternator terminal and was around 14-15v.

There were 3 reoccurring fault codes:
U012D lost communication with generator control module.

U0285 lost communication with active grille air shutter module.

P165B grille shutter performance/stuck.


I proceeded to check fuses f35 (5a) air shutter & f22 (15a) battery monitoring system. I then checked the operation of the grille shutters (found to be non operational). To test operation they should be open when the engine is off and closed when the engine is running from cold. I also checked for free moving of the shutters and for the possibility of debris blocking it from functioning.

I removed the single wire signal plug from the back of the alternator to check for damage, broken wire, water ingress or corrosion etc (no fault found). I then checked for voltage at the signal wire, the wire should show roughly 9v with the engine running and the wire unplugged (mine was 8.6v). I then plugged the wire back into the alternator and probed the wire to find that the voltage then dropped to around 1.5v indicating a short or fault with the alternators internals, the alternator was diagnosed with a regulator fault by a specialist.

The alternator was replaced, afterward the battery light remained illuminated, however the alternators signal wire was showing 9v while plugged in. I proceeded to check grille shutter plugs (x2) for corrosion, broken wire, water ingress etc but no fault found. I checked the two outside wires of the plug for 12v ignition live and the test proved fine no fault found. I checked the ground wire to the plug and the resistance & continuity readings were fine, then I tested the central signal data wire (blue/brown?) for the 9v, as this wire shares the same circuit as the alternator signal wire.

The signal wire at the air shutter plug was showing 0v with the engine running, I tested the wire with the alternator signal plug for continuity and resistance with no fault found. I then tested the wire from the pcm plug for 9 v with the engine running and there was correct voltage, so I bridged the alternator signal wire to the central data wire for the air grille shutters which solved the battery light and grille shutter fault.

In this case there must have been a broken/damaged wire somewhere in the lin bus wire from the pcm to the active air grille shutter motor. Strange though as the continuity readings were fine. I’d recommend removing both the signal plug from the alternator and the grille shutter plug and testing for voltage at both of the signal wires with the engine running. If there’s a significant voltage difference to 9v I’d suggest a PCM fault, if there is 9v there then plug one in at a time and probe the wire after the plug, if the voltage drops from 9v then that would suggest a fault with the motor or alternator respectively.

Part number for grille shutter motor:
Bm51-8476-
This motor/actuator is also used on other ford/Volvo etc models for other uses such as heater control flaps etc.

Here’s a link to the tsb I mentioned in the video: https://www.scribd.com/document/35166...

Here’s a link to a fuse layout for this car:
https://www.google.com/amp/s/fuse-box...

Random focus grill shutter wiring diagram:
https://f01.justanswer.com/shawn24_91...

Grille shutter removal procedure:
https://f01.justanswer.com/shawn24_91...

Grille shutter motor replacement:
https://f01.justanswer.com/shawn24_91...