Peugeot 207 CC 1.6 HDi 2009 – ABS/ESP U1221

[Radaresat]

Hello,

I am trying to diagnose an ABS/ESP issue on my 2009 Peugeot 207 CC 1.6 HDi.

VIN last 5 digits: 25762

Diagbox previously showed the following ABS fault:

U1221 – Fault absence of communication with the electric power steering ECU

* Status: Permanent fault
* Characterisation: Data invalid

At the time the fault was stored, the ABS ECU supply voltage was showing only 7.4 V.

Later, in live data, the ABS ECU Supply voltage was around 8.8–10.4 V, while the BSI and battery voltage were normal.

Multimeter readings:

* Engine off: 12.47 V
* Engine running: 14.44 V

So the battery and alternator charging voltage appear normal.

I also checked the engine bay fuse box. It is completely dry, with no obvious water ingress, corrosion or oxidation.

According to the maxi-fuse chart:

* MF2 – 20/30 A – ABS/ESP pump
* MF3 – 20/30 A – ABS/ESP solenoid valves
* MF10 – 80 A – Electric power steering

The relevant fuses and holders look physically clean, and I will also check them for voltage drop.

The car drives normally and I do not constantly get an ABS/ESP warning while driving, but I am not fully sure whether the ABS is actually functioning correctly.

I am considering the following possibilities:

* ABS ECU/pump unit may have been replaced previously and not correctly telecoded.
* Electric power steering ECU/rack may have been replaced and not correctly configured.
* Voltage drop in the ABS ECU power supply, connector or ground.
* Internal fault in the ABS ECU voltage sensing circuit.

The engine ECU also previously stored:
P0704, P1351, P0299, P1435, P1434

Has anyone seen this combination of U1221 + low ABS ECU supply voltage on a Peugeot 207?

Also, if the ABS unit or electric power steering unit has been replaced, does it require Diagbox telecoding/configuration or calibration?

Any advice on what to check next would be appreciated.

Thanks.

[Huskyxantia]

I had a 206cc same thing my problem was the loom from the abs pump had 5 wires exposed due to road grit and they would touch now amd again then the faults would come up on the display . I cut the bad out then soldered the joints back together then covered them in black waterproof tape , problem sorted

[Radaresat]

I think this connector is supposed to look like this; it seems to have some kind of protective coating or material on it. At least, that’s what GPT says.

I checked the top and bottom points with a multimeter and couldn’t find any break in continuity. However, the battery voltage drops as low as 8.77 V while cranking.

Tomorrow I’m going to check it with Diagbox. Also, I couldn’t find the MF9 and MF10 fuses.

[Radaresat]

I did a more thorough check and found that the ground connections were very poor. I cleaned them, but it’s already late now, so I’ll continue checking everything tomorrow.

[Huskyxantia]

That yellow wire in the loom looks spilt undo the back tape around the loom check each wire without the tape on that's how I found my problem

[Radaresat]

I am confident that the car's battery is in very poor condition. I am getting code U1331 along with a power steering fault. I tried to recode it, but couldn't find the option in DiagBox. There is also no communication with the ESP module, and everything is a mess right now. Do you think I need to buy a new battery? I checked the cables and they are intact.