Electrical Problems

[MeridianMan]

Hello one and all,
I have always been a great fan of Citroen cars, and have owned a couple or three in the past. I have never though had any problems with the electrics on any of my previous cars. I now own a 2003 C5 exclusive estate and have been told by "people" that they are the very worst in this department, being on a par with Italian cars who are notoriously bad with their wiring and computers.
What are the facts? Are they difficult cars to look after electrically, and in what departments are they better than others. I say this as I am having some problems with the rear doors locking and unlocking, some time they work, other times not. The nearside door appears to be the worse as it refuses to open from either the outside or inside most of the time, while the off side door at least will always open from the inside, but not from outside, a kind of child lock in reverse situation.
Anyone else out there had similar experiences.

many thanks in advance;

Ian.

[Hell Razor5543]

While the C series Citroens have more in the way of electronics than their predecessors, it would be unfair to say they are more unreliable. Certain things can 'upset' them, especially a failing battery (they are VERY sensitive to this). One thing that can help clear up glitches (as opposed to actual problems) is a BSi reset (a bit like letting a PC to a full, clean shut down, as opposed to just pulling the plug). There are a lot of ECUs in one form or another in there, and they do not shut down when you turn off the ignition, but go into a state of standby (which means that if a glitch has occurred it does not get flushed out). Here is how to do the BSi reset;

https://www.frenchcarforum.co.uk/forum/ ... 11&t=40407

However, I had a problem with my previous car (a Xantia), in that both rear doors would not respond to the central locking. One could be locked/unlocked manually, but the other was deadlocked. It turned out there was failed wiring in the door concertina grommets. I added in some lengths of wiring to the damaged wires, and the doors then ended up back on the central locking system.

[GiveMeABreak]

The C5 in common with many modern vehicles uses a multiplexed wiring system. Essentially there are about 20+ ECUs or electronic control modules located about the vehicle. These include the ECUs for the Injection, Air Con., BHI (Suspension), ABS/ESP/ASR, Radio Head Unit, Doors etc. They are all linked to the BSI or Built in Systems Interface which acts as the controller. There are at least 4 interdependent networks that are used to connect these up runnimg at different speeds depending on priority of the system.

The BSI basically codes and decodes the data going to and from these modules using binary. The BSI can command a function by sending out a specific code along a set of wires for a specific module to pick up. In doing so, wiring can be reduced by at least 30%, but it also allows for a lot more functionality. There is also additional reliability in that for some key systems where a single wire of a pair becomes damaged, the other channel can continue to carry the signals.

What people tend to forget is that as the car contains lots if mini controllers and a main CPU (BSI), it can be temperamental when it comes to low power, or disconnecting the battery without allowing the components to close down properly, just like your PC if you pull the plug without shutting it down properly first!

Once you understand how these operate together it just a matter of observing some basic procedures when disconnecting and reconnecting the battery and performing this procedure periodically.

An example of how this is different to a conventional system:

On a non multiplexed car, take the electric windows for example, you press a button one way it goes up, press it the other way it goes down, that's it. On your C5 for example, the BSI can look at information from the rain sensing wiper ECU and determine the severity of rain from the speed the wipers are going. It can then send out a signal to the driver's door module to determine if the windows are open, and if so, command them to close, so you don't get wet. Similarly, if you have a sequential electric sunroof, the BSI can determine the speed of the car from the ABS ECU and if it determines the sunroof is open at too wide a setting for the speed of the car, it will command it to close. Another example on Hydractive 3+ Citroens is lowering or raising the suspension within certain parameters according to the road conditions and the speed of the vehicle automatically.

These are a few simplified examples of the sort of logic that is behind the electrics on modern multiplexed vehicles, but the C5 in this particular case.

[Richard_C]

Agree with all of the above. Your door problem could be wiring to the door where it goes through the rubber grommet, or sometimes even a simple physical problem - the solenoid tries to unlock but its all a bit gummed up in there and sometimes fails. Place ear to door, un lock/lock and if there is no sound of activity its likely the wiring.

In terms of general electrical faults 3 things can help with Citroen and other similarly equipped cars:

Battery (and its connections) - as Hellrazor says, it can appear to be fine and start the car well enough but even a small voltage drop can confuse things.

Earthing - example I had all kinds of bulb out warnings on my old C3, bulbs fine, could measure 12v at the bulb holders, but the earth connection was corroded so wouldn't cope with the current of 2 bulbs on at once - e.g. sidelights and indicator. Always check/think about earth as well as supply.

A cup of coffee. The cure for many ailments (even cured an erratic auto gearbox ecu on my old SAAB). Here's how it works. You disconnect the battery. You take your time to enjoy a really good cup of coffee - have a biscuit as well, half an hour should do it. Then reconnect battery using the proper procedure for the car. Magic!