C3 Picasso 2009 Braking System Faulty

[Airdman65]

Hi, my first post on here and hopefully I'll get some help from you kind people. I have a 2009 C3 Picasso 1.4 VTR+ which has been causing me a massive headache. It died las August after losing power when being driven, it also had a Braking System Faulty message. I'm in the Outer Hebrides and the garages wouldn't touch the car! I have managed to get the car started, I changed the BSM module as I suspected the fuel pump was not getting the 12v. This worked nicely and now I am looking at the Braking System Faulty error. The car drives OK and brakes function normally. I ran a DTC with my Topdon and it found the following:

ABS: C1389, U1318, U1308, U1108. (Brake fluid level is OK)
BSI: F40A, A4BF, A4C8, F5FF, A9B7 - this one looks rather nasty!
Power Steering: U1108, U1308
Engine wiring housing: A9B7

VIN:VF7**************[VIN obfuscated, can be read by forum staff]
C3 Picasso (A58)

I can see no obvious damage to wiring in the engine bay, all fuses checked and re-seated, battery is new and charging is correct voltage when measured. Any help greatly appreciated before I pull all my hair out!! Thanks.

[mickthemaverick]

If you could add the description of each of those fault codes you may get some feedback. We just don't have time to go through that many codes for every post like this that appears.

[Airdman65]

I knew I should have done that!

Here goes:

Engine management ecu
DTC Description Status
P0215 Fault : Principal relay control-Relay malfunction Intermittent fault
P0011 Inlet camshaft dephasing fault-Coherence Permanent fault
Anti-lock Braking System (ABS) or Electronic Stability Program (ESP)
DTC Description Status
C1389 Brake fluid level low fault-Not characterised Permanent fault
U1308 Engine ecu operating fault-Not characterised Permanent fault
U1318 Operating faults due to the built-in systems interface-Not characterised Permanent fault
U1108 Fault: no communication with the engine ecu-No signal Permanent fault
Built-in systems interface
DTC Description Status
A4BF Fault: illumination of the rear LH brake lamp-Short circuit to positive
A4C8 Left-hand reversing lamp lighting fault.-Short circuit to positive
F5FF Unexpected re-initialisation fault coming from the BSI.-Not characterised
A9B7 Engine wiring housing : Ignition positive (+APC) relay or relay output
harness fault-Short circuit to positive.
Power steering
Page 2
Report Number : TD1776099801
Date Created : 2026-04-13
SN: 110513X5F503G8
TOPDON ID: KVKD0USS4X
DTC Description Status
U1108 Fault: internal combustion engine status information-Not characterised Permanent
U1308 Fault: internal combustion engine status information-Not characterised Permanent
Engine wiring housing
DTC Description Status
A9B7 Ignition positive (+APC) relay or relay output harness fault-Short circuit
to positive
Radio
DTC Description Status
B900 Fault on antenna input no 1(white connector) .-Short circuit to earth.
F905 Fault on auxiliary audio input n° 1.-Not characterised.

[mickthemaverick]

With that many and varied faults the first thing I would suggest is that you check the various earth straps from battery to body and chassis to engine and gearbox etc. Ensure there is no corrosion in the connectors around the fuseboxes and then reset all the faults and rescan.

[Airdman65]

Will do, the more I think about it, I'm sure it'll be a loom problem. Two BSMs used and the APC+ fault remains, so unless the spare BSM has a relay fault, it probably is wiring. I'll check the earths as you suggest. Thanks.

[PaulC5]

Have you deleted the fault codes and then seen what comes back, just asking in case they are old ones.

[Airdman65]

Hi, yes all deleted, but the APC+ remains as does the ABS. Just been working on it, earths all look in good condition. Measured the battery voltage between earth and the BSM bolt, I assumed this bolt was an earth connection for the BSM. I see the battery voltage here, is it an earth on the BSM?

[Airdman65]

A wiring diagram would help if anyone has one to share.

[Airdman65]

Update, checked for parasitic drain as the battery too low to start this morning. Using my trusty AVO, 2 Amps drain measured. Disconnected each large plug from the BSM in turn and no change. Time to work my way through all the fuses to find the culprit.

[Airdman65]

All fuses removed (bonnet and cabin) one by one whilst monitoring the AVO for current drawn. Nothing changed at all. Removed BSM in total and under where the MF fuses are, checked all OK. Thought I'd check the brake light switch so pushed pedal and increase in current drawn - need to check this further.
Checked the brake fluid sensor cable and removed, ran OBD and shows it high - disconnected so correct.
Replaced and cleared DTCs. The APC+ relay output and harness faults still showing but only as minor. ABS faults remain as does the Brake System Faulty warning.

Next steps are to find some info on the foot brake light switch, anyone have any details?

Cheers

[Paul-R]

Generally speaking the master cylinder remains on the LH side of the car on RHD cars and the effort is transmitted from the brake pedal to the master cylinder push rod with a strong tube across the car. The brake switch is then on the LH side of the, above the passenger's legs. That's the best I can do.

[Airdman65]

Thanks, I checked to see the lights operate correctly when i put the foot brake on. All working OK so it's back to the drawing board. A real head scratcher this one!

[mickthemaverick]

Exactly where had you connected the AVO for the fuse out tests?

[Airdman65]

One probe on the detached +ve cable and the other on the battery post so the meter is in series and showing 2 amps on DC A setting. Remove each fuse in turn but no change in current drawn.

[mickthemaverick]

Then that suggests you have a leakage to earth from the main positive cable to the fuseboxes, possibly the fault lies on the loom route to the fuses.