C5 Computer Problems

[Guest ems69]

I have a 03 C5. It is showing an Abs and break fault lights. At the same time the spedo stopped working and there is now a juddering going up through the gears like im in the wrong gear for the speed. I took it for a diagnostic, my cpu isnt talking but they checked my breaks and said they were fine but the abs was not working. But no one can tell me what the fault is. Do I need to buy a new motherboard ? but as i understand it, the faults I have are controlled by various cpu's adn so I am at a loss as to where to start.

Has anyone had these sort of problems or could offer any advice ?

[Randombloke]

Measure the battery voltage when the engine is not running, and when it's running.

 

Check all the electrical connections but DO NOT disconnect the battery without following the procedure elsewhere on the forum.

 

Lots of problems with the C5 can be caused by low battery volts, the battery may still crank fast, but low voltage can allow spikes into sensors. If the battery does not seem too healthy then replace it. 12.6 to 13.2 volts engine off, 13.6 to 14.4V engine on - this is what I get with mine. Sometimes it's lower on switch on because the electric suspension pump runs.

 

If the battery is fine then consider the reset process outlined elsewhere on this forum.

 

Check the connections to all the ABS sensors from the wiring loom are OK, and if not maybe give them a clean, but be careful not to break or damage any connectors. Check the ABS fuse.

 

Coastline?

[paul.h]

Abs and speedo faults may be related since the abs system is used on many cars to give the cars speed. The fault could be something such as a wire problem or a faulty abs sensor or a driveshaft problem (which may also give juddering). If the front brake pads are ok the pad wear sensor wiring could be faulty to give the brake fault light (but you would also get the Service message lit up - I did) - you could unplug the wires at the front brake calipers to check if the warning goes. The juddering may also be a separate fault such as a clutch or flywheel problem.

 

What model car and engine is it and how many miles ?

 

Was the diagnostic check done by a Citroen dealer or elsewhere but still using the Citroen equipment ?

[coastline taxis]

wow what a week weve had very very busy both in the garage and the taxis (very much needed as its been really quiete recently). Anyway back to this post

the stepper motors on the speedo are prone to packing in on a c5 so you cant assume its connected to the abs fault although it most probaly is by the sounds of it a quick test will sharp show one way or the other. zero your trip display and take the car for a mile drive if it shows the mile up on the trip meter then its your stepper motor if its still on zero then the fault is connected.

 

Abs fault youl not get much out of the ecu by going into the engine side of things. Youl need a decent scanner or lexia and go into the abs side then live data then wheel speed take it for a drive and youl see if all 4 wheels are returning a signal.

 

What diagnostic machine are you using/does it do citroen if it does then you need to check the fuse for the obd port(its in the glove box right hand side of the fuses 10 amp i think). it sounds like it wasnt a citroen dealer you took the car to as they would always give you options of where to start next. So you need to ask whoever it was that done the diagnostic if theyve had any experience with citroens if they havnt then for the sake of your pocket you need to find someone who does