Debugging multiple electrical faults

[DennyLoi83]

I've done some reading on the forums, and this appears to happen to a few people, but my situation has a few slight differences.

In summary, I get the ESP system error, parking brake error, ABS system error simultaneously. They all appear at the same time. The anti-pollution system error has been intermittent for some time. It comes for a couple of days, and then disappears for a couple of weeks.

I have read that this is typically a result of either:

• ABS sensor failure

• EGR valve problem

• Something to do with indicator lights

I am having trouble debugging this at is only happens when driving at high (ish) speeds, typically around 55mph - 60mph. It therefore only appears when on the motorway. When I turn the engine off and on again, all errors clear. When the errors are present, the car drives absolutely fine and there is no difference whatsoever to performance. It has never occurred at speeds of less that 50mph.

I was under the impression that this was being caused by high revs, but this isn't the case. I have the habit of free-wheeling on long downhill stretches, and the errors have also also appeared with 0 revs but a speed of around 55mph.

The car is a 2010 Citroen C4.

Thanks in advance.

[DennyLoi83]

Anyone have any ideas what the issue may be?

[GiveMeABreak]

Well bear in mind that the wheel speed sensors are integral to the ESP / ABS ECU which in turn controls the electronic parking brake. So a fault with even one wheel sensor will disable many ESP functions such hill start assist, cruise control and of course some features of the ABS system itself as you would expect for safety reasons. So it's easy to see why you would get all those faults showing.

As for the EGR - this can be a tricky one - it may or may not be related - RichardW has some experience of this issue on the Picasso, so he may chip in if he sees this.

But if, as you say, the warning is still coming up regardless of engine revs and even when coasting in neutral, then I would initially be focussing on wheel sensors. A Diagbox diagnostic is your best bet in order to get a better idea. If it is a wheel sensor, it should be able to tell you which one.

[RichardW]

1.6 HDi? It'll be the EGR valve causing the trouble.

[DennyLoi83]

Thanks guys. The car is petrol:

Citroën Grand C4 Picasso
1.6 16V VTi VTR Plus 5d 2009/59

Does that help in narrowing it down at all? Perhaps my best bet would be to 'break down' and call the AA so they can read the error codes there and then.

[DennyLoi83]

I should also add the following information:

The ECU under the bonnet, by the battery, burnt out in July and I replaced it with another one from Ebay. After that, these electrical issues (as described in the other post) starting happening. I then replaced the ECU unit with another one from Ebay, but the issues persisted. Both ECU's had the same part numbers as the faulty one. It would seem weird if both ECUs were faulty.

After that, I replaced the radiator fan relay as the radiator fan stopped working. The error existed both before and after I did this.

I've just been ignoring the errors and driving the car as normal as it doesn't seem to make any different to performance. The only noticeable difference is that the handbrake doesn't automatically apply.

[GiveMeABreak]

To avoid duplication, this topic locked, but is continued here:

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