Multiple warning lights

[Justmee]

Hi All,

Just joined to help daughters get car back on the road.
2014 C4 picasso (possibly a grande)
vin3A9HC8EJ577192
It has the common ABS, tyre pressue, parking brake, stability control ect ect warning light combo.
Live date shows speed on 3 wheels but not the OSR.

Mine & the MOT garage's OBD says right rear ABS sensor.
Changed sensor, no change.
Googled issue & found that the rear wiring is an issue so fitted about 18" of new cable, no change.
Fitted new hub, no change.
Replaced 5 amp fuse in the panel in front of battery, seems to have helped stop some of the brake warnings.
Looking round this forum & it seems its worth replacing the wire to the terminal block under the rear seat.

Now the questions.
What voltage should get to the rear sensors? Both sides are getting about 10v. Tested with sensor unplugged & to ground and the return wire. Return wire to ground gives a few mv.
What resistance should a good rear sensor have?
Is it possible that both the OBD readers are confusing left & right?
If replacing the wire is it worth going further forward & if so to where?
All the way to the pump / module? Which I think is in the OSF wheel arch / inner wing.
Do the wires stay the same colour? In this case yellow & green at the rear sensor.
As well as the code for the OSR sensor it has a code for C1391 non confirmation of engine torque in the ABS module scan.


Thank you inadvance for all & any help given

[PaulC5]

Was the replacement sensor a Citroen one or a copy part ?

[Justmee]

A copy.

[PaulC5]

Try swapping the copy part with one of the other ones to see if the fault moves and suggests the sensor is at fault. It is also possible the corner sensors are different to the central ones despite looking similar.

[Justmee]

Try swapping the copy part with one of the other ones to see if the fault moves and suggests the sensor is at fault. It is also possible the corner sensors are different to the central ones despite looking similar.

That was the plan to swap them as a first job tomorow.

[Justmee]

Any tips on finding the connector under the rear seat & the connector on the abs unit?

[Justmee]

Just a thought, on the short replacement wire I soldered in.

Its not twisted pair.

Will that matter for such a short section?

[Justmee]

Just tested left sensor and I am getting 2.7m ohm. The new sensor is 0.5m ohm.
Does that point to the left sensor being the faulty one or the new one is faulty or the wrong one?

[Justmee]

Voltage readings,
Osr (with faulty code) 10v
Nsr no code 11v

[Justmee]

To close this off.
All fixed.

In the end it was the wire to the plug under the center seat.

Ran new wire (not as bad a job as you might think).

Voltage at the plug was virtually the same but I'm guessing that the voltage colapsed under load due to the duff wire.

Now just got to do the front discs and pads, Eolys fluid and one (snapped off) locking wheel nut.

[Justmee]

A few pics cos we all love pics.

Two seats out, center & NSR allws access to the plug.
Remember to disconnect the wires (2 from center & 1 from NSR).

Under the carpet is the 4 wire plug. The yellow green wires are for the OSR ABS sensor.

First I tested the voltage & then did a simple bypass using crimped connectors. Once happy it worked I ran the cable & soldered all the joints.

Proof of the pudding, no warnings on the dash.

[wurlycorner]

Well done finding and sorting it and even better for writing it up, with pics!