(another) C4 ABS problem

[TBWidow]

Hello you all.

For the last couple of weeks i've been dealing with an ABS/ESP fault in my 2011 C4 B7 1.6 E-hdi.
It started by giving a STOP/ Service message, with the so known ABS, ESP, Anti roll back and engine malfunction messages in the multifunction display, that I've read so many times here in the forum. It also did some things that I haven't seen here: I lost speed indicator, milage, trip odo, autonomy, the engine not running well at low RPM, even parking sensors do not work. Also when I stop the engine and lock the car, the radiator fan keeps running for quite some time (low velocity), even when cold.

I've read the faults (friends mechanic AUTEL) and they were:
-Lost of communication with ABS module
-BSI detected wrong data packages in CAN

From the experience I have in car electronics, from dealing with them some years ago, I'm pointing to the ABS module.
But today I was looking to the Xmas tree that my dashboard became and the only red error is the (!), which made check the float switch in the secundary brake/cluctch reservoir; I checked for the presence of ground in the ABS ECU pin 4 as per schematic and there was no ground. Next I've bypassed the float switch with a piece of wire and ground got to pin 4. I tougth that somehow the problem was there, but not. Same errors on starting up. I did not clear any errors because I only have a ELM327 and Torque app in my phone, but I read them and they were:

-U0121- The U0121 code is triggered when the ECM detects a loss of communication with the ABS control module
-U0422- The definition of code U0422 is “Invalid Data Received From Body Control Module.
-U0073- The U0073 error code stands for "Control Module Communication Bus 'A' Off."
-U3FFF- Fuel High Pressure Circuit. Fuel Pressure Lower than The Reference Value

Since the ABS ECU plug was out, I also checked for grounds and positive power to the module, which I think are all in the good places.
The schematic I based on was one from this post: viewtopic.php?t=68032, that I know that is not the same car.
Also checked CAN bus values, 61 ohm, with ABS ECU plug disconnected 120 ohm.


So, what do you all think I'm up to?
ABS module?
Faulty wiring?
Dodgy BSI?

I think the faults would clear or at least behave different if the source of the problem went away, but do you recon I need a good reset tool to start from scratch?

If get an ABS module with the same reference as mine, would it be plug and play or would it have to be coded?
My VIN, as I've seen you ask many times, is VF7**************[VIN obfuscated, can be read by forum staff].

Thank you all in advance!!

[PaulC5]

Have you checked the battery voltage, if low it can give odd electrical problems. You could also try a bsi reset.
If you give the fault code definitions it will help with replies since it saves people having to look them up for you.

[TBWidow]

I've updated the error code description. Battery voltage is fine: 12V engine not running and 14.1V engine running.
I'll try the BSI reset this evening.
Thanks!

[mickthemaverick]

Did you check the battery with no engine but headlamps on main beam and audio system on? If that drops below 12V then your battery is still suspect, if so an overnight charge is the first step and then do the same tests when the charge is finished.

[wheeler]

If get an ABS module with the same reference as mine, would it be plug and play or would it have to be coded?
My VIN, as I've seen you ask many times, is VF7**************[VIN obfuscated, can be read by forum staff].

Its not so much coding, its configuration. 2 cars could have the same ABS unit fitted but the cars may be different spec like tyre size or gearbox type. Its only basic configuration like Tyre size Gearbox type & engine.

[PaulC5]

I've updated the error code description. Battery voltage is fine: 12V engine not running and 14.1V engine running.
I'll try the BSI reset this evening.
Thanks!

12 volts is too low, should be 12.7 volts if fully charged and before the first start of the day. See what you get after charging it up. If the battery is old it might also be low on capacity so when starting the engine its voltage could drop too far.

[TBWidow]

I've updated the error code description. Battery voltage is fine: 12V engine not running and 14.1V engine running.
I'll try the BSI reset this evening.
Thanks!

12 volts is too low, should be 12.7 volts if fully charged and before the first start of the day. See what you get after charging it up. If the battery is old it might also be low on capacity so when starting the engine its voltage could drop too far.

I don't think it's too low. Remember that the radiator fan keeps running and draining the battery. I've measured at that time. The car starts beautifully.
Also, even when the car had a bad battery, 2 or 3 years ago, before swapping it, it never trown an error up.

[Rp0thejester]

Easy fix, ignore it! My fan decides to occasionally constantly run even if cold, stop and restart engine several times, if that doesn't work pull battery. I've had ABS, Speed limiter/cruise control warnings etc etc etc, it's the usual Citroen electrical gremlins.

[TBWidow]

Easy fix, ignore it! My fan decides to occasionally constantly run even if cold, stop and restart engine several times, if that doesn't work pull battery. I've had ABS, Speed limiter/cruise control warnings etc etc etc, it's the usual Citroen electrical gremlins.

It's easy to ignore the fan, but driving without speedometer isn't so easy...

[myglaren]

Easy fix, ignore it! My fan decides to occasionally constantly run even if cold, stop and restart engine several times, if that doesn't work pull battery. I've had ABS, Speed limiter/cruise control warnings etc etc etc, it's the usual Citroen electrical gremlins.

It's easy to ignore the fan, but driving without speedometer isn't so easy...

Satnav as a bodge for that?

[RichardW]

My guess is that this isn't anything to do with the ABS. Scan the engine ECU for faults. You noted one above about low fuel pressure - is this in the engine ECU? When was the fuel filter last changed?

[PaulC5]

The engine fan sometimes runs on our cars for a while after switching off and I suspect it is something to do with the dpf being regenerated, so in our case normal.

[TBWidow]

My guess is that this isn't anything to do with the ABS. Scan the engine ECU for faults. You noted one above about low fuel pressure - is this in the engine ECU? When was the fuel filter last changed?

10kkm ago

[TBWidow]

Hello again. So to develop this thread, I got hand on a ABS module with the same part number as mine. Unplugged mine and plugged the other one (only the plug, not the brake lines) . Now I don't have any errors on Torque, regained my speedo. But shows error in ESP and ASR. I understand that this new unit needs to be coded.
In another post, Givemeabreak left this warning:
"A word of warning - make sure you record or take a screenshot of all the existing parameters in the ABS / ESP ECU before replacing the unit! There are several options when reconfiguring - if you get the wrong ones, it will not function. This mist be done before removing the old unit."
I understand it, but since I don't have communication with the old module, how can I read the existing parameters? Any thoughts? Thanks in advance

[wheeler]

There are only a few parameters to configure in the ABS system if it remember right, Pretty sure you will be able to do it 'by eye'.
Tyre size, Gearbox type & engine type.