Citroen C5 HDi Estate ABS ECM/modulator

[CitroenJohn]

Hi there, I have can ABS fault / warning on my 2003 C5 Hdi Estate. I have checked all the fuses, connectors, sensors etc and all seems ok. The car has been sat around for ten months as unfortunately I had a seizure last June and was diagnosed with epilepsy and had to surrender my driving licence. I am going to get my licence back and the car on the road after 12 months of being seizure free. I have been exercising the car regularly in our unadopted road but the warning light just decided to come on a couple of occasions ago....

Today I had a guy who runs a garage connect his machine to the OBD connector in the glove box. It says that there is a permanent fault with the main ABS ECM/pump behind the battery. I have just stripped things down so I could check the connector and other fuse in the fuse box i hadn't previously found and all seems ok. I am looking at second hand units on eBay as i need to get the car through an MOT as cheaply as possible if I can-I am a driving instructor by trade and, of course, with my licence went my job and income, so am pretty skint! I cured a load of problems last year and put a new battery on just before I lost my licence and the car has only done 200 miles since the last MOT!

The Haynes manual says that new ECMs must be initialised and programmed using Citroen dedicated diagnostic equipment. Knowing Haynes manuals, i suspect that this is not true and that I could fit a second hand unit without any electronic problems? Can anyone please tell me if I could expect any problems replacing the unit? Thanks in advance, John.

[demag]

Hi John I would say Haynes might be right although I'm no expert. You might need a session on a Lexia to get everything talking. There might be some members up your way who would do a Lexia scan for you.

[ekjdm14]

Just a thought (and maybe stating the obvious again, as dictated by my lack of experience with these more modern cars lol) but is the battery fully charged? If it's only done 200 miles in a year and presumably a lot of shorter runs then it could be a bit weak which I believe causes all kinds of spurious faults with these.

Here's hoping, a battery charger is a lot cheaper than an ABS mod. Anyway

[CitroenJohn]

Hi guys, sorry for the slow reply but i have only just found your messages, so thanks for your suggestions. I keep the battery charged up well and it starts the car up no problem. I got a second hand ABS unit on eBay and fitted it ok. However, the ABS light and warning has not gone out, so I lived in hope that the fault message would be cleared when connected the the diagnostic machine again.I bled the braking system twice over, effecting a complete fluid change. I also fitted new seal kits to both front calipers as one was leaking by the piston and the other was a bit sticky. Having said that, the brake pedal seems to very gradually sink if you keep your foot on it with the engine running (although it doesn't do that when the engine is off)!!!??

Tonight my friend from the garage came back with his £2000 worth of test equipment and plugged it in. The permanent fault is still showing though and his machine couldn't seem to cancel it. He took the car down the road a bit with me beside him while i checked on the machine that there was a speed readout from all the ABS wheel sensors, so I know that they are all ok. So for some unknown reason I am no further forward and am getting pretty peed off and stressed out through spending loads of time and throwing money at the job. I really need this car ready for the road by the time i get my licence back but right now i feel like chucking it in a crusher and crying into my pillow!

I can't remember the make of diagnostic kit we have been using, but he said he would bring his Snap On test machine next week, because he said one machine will work on a car when another one won't. Or perhaps it would take a Lexia to communicate with the ABS ECM.....I noticed that myglaren posted a list of Lexia owners on here and that there is one guy in the Leeds/Bradford area, if he were able to come to me. Or.....maybe i have purchased a faulty unit from eBay !! I will get in touch with them and ask if they knew the unit worked before they stripped the car it came off - (not that they are likely to say it didn't)! Any suggestions or input? I would be glad to hear from you.

[BX]

Permanent faults on any car generally cannot be cleared without first of all correcting the problem. Some of them will clear and instantly reappear the next time the ignition is turned on. If it turns out that the abs unit is at fault you can fit a used one plug and play. You can just plug in the replacement unit and ensure it is mot throwing up faults before fitting it. Compare the numbers on the existing and replacement units.You need a diagnostic unit to bleed it but most of them (except for basic code readers) can do that. The only programming is for wheel and tyre size as that affects the accuracy of the speedometer.

[RichardW]

You really need to know what the exact fault is - short circuit; no dialogue; internal fault; lack of speed input etc etc. If you've swapped the unit and the same fault persists, then it is somewhere else - the wiring to / from the unit, or the underbonnet fuse box are suspects (although these are not so troublesome on early cars AFAIK).

[BX]

As Richard said you need to know what the fault is. Then you can look into solving it. The lexia/diagbox is the be all and end all on Citroën. However most of the multi purpose units (launch, snap on, Delphi, auto com, autel, etc) will do at least 95% of what any mechanic needs. Some are better on European cars (Delphi) some are better on Asian cars (Autel)

[CitroenJohn]

We have now tried the Snap On Tester as well, without any more success. When you say you need a diagnostic tool to bleed the replacement unit, does that mean the tool bleeds the unit automatically within the closed braking system or do you use it in conjunction with bleeding the system manually at the wheels?
I am currently trying to contact jimmymarsbar from this forum at http://www.diagnosticshub.com in the hope that he can come and sort everything out with his Lexia tester.

[BX]

The tester should have a bleed program which prompts you. Failing that, activate the abs pump using the tool and continue to bleed in the normal way.
What do you mean by "We have now tried the Snap On Tester as well, without any more success". Will it communicate with the abs system at all.

[CitroenJohn]

The Snap On tester recognises a fault on the ABS unit but it doesn't offer any further options - i.e. to communicate with it / cancel fixed faults or do anything else.
I can imagine that there might be air in the ABS pump unit, which cannot be purged by bleeding in the conventional manner (without a Lexia telling the unit what to do) as the pedal feels rather soft when pressed and does seem to sink gradually when the engine is running.

[BX]

Yes but if it sees a fault it should give some information in the form of a code or description. I do not have any of the snap on diagnostics but I do have an old autel code reader. That is all it does read the codes (engine, abs, srs and transmission) can clear them if the fault is repaired and gives live engine data. I also have an autel maxidas which reads codes on most systems, gives live data on most systems, gives the option to activate certain components and can do a certain amount of programming such as keys.
I also have auto com which does basically the same but is better on European cars e.g. vag, psa, fiat, Renault. The maxidas gives better coverage on Asian cars such as Toyota, Hyundai etc.
So far I have never had the situation where the diagnostics identified the presence of a fault without giving some information. The term unknown fault sometimes appears. This means that the machine does not have a description to match the fault code. However it would always give the code. Professor Google usually will give the missing information.
In your case we have no idea what we are dealing with. It may be an internal fault such as a faulty solenoid in the abs unit or it may be a missing supply. The logic appears to be supplied as you could read the speed on the 4 wheel sensors, but what about supplies for the solenoid valves or the pump?

[CitroenJohn]

Thanks for your thoughts on this problem and sorry for the delay in posting but it has taken me time to get things together and have another go at curing the ABS problem. I suppose there could be a fault in the electrical supply to the ABS pump but I'm not sure how to check that. I have now bought myself a refurbished laptop (which I needed anyway) and the Diabox interface leads and Diagbox software for Lexia and Peugeot in order to sort the problem out myself - or so I hoped! Having installed the Diabox software and after doing a global test on the car The Lexia comes up with a permanent fault on the ABS recirculation pump. This is a replacement pump which I bought second hand on eBay and the vendor assured me that it had been working ok on the donor car (if I can believe him)! It seemed logical to go through the brake bleeding process with the Lexia and i have been doing that this evening. I followed the prompts to bleed the front and rear brakes and then it came up with a screen telling me to "switch on the recirculation pump". Seeing as i have no idea how one does that i pressed enter to go to the next screen which comes up with "communication error" and terminates the bleeding process. How on earth am i supposed to turn on the pump, I wonder? If I could successfully complete the bleed then the problem might be cured but there is no way without knowing how to do what the Lexia means