Citroen C5 iii 2009

[davidm3836]

Hi there,

Looking for assistance if possible. I have a 2009 Citroen C5 iii, it has an issue which is driving me mad. When I try and start the car I get a message saying “braking system failure”, and the car will not start. It won’t even crank, I can hear a relay clicking in the internal fuse box when I turn the key but that’s all I’m getting. Also when this message is displayed it blocks access to scanning the car through the OBD port. Rarely on occasion this message will disappear on its own then the car will start and drive perfectly! I have this morning changed the brake switch but no change, checked all relevant fuses internally and in engine bay. Anybody got any ideas? It’s a manual car and manual handbrake too. Thanks

[GiveMeABreak]

Without a diagnostic code it won't be easy to assist you. It could be anything to do with the braking or associated components as a lot of these systems are interlinked.

For example a faulty ABS wheel sensor, a fuse or the ABS / ESP module etc. etc.

Best if you can connect up Lexia or diagbox and get some fault codes, then pop them up.

[davidm3836]

Thanks for the reply Marc, the issue is the car won’t let me hook up to it with any device. Nothing sees the car when that message is present. Really strange. Checked all fuses too. I thought even though that message is displaying to show the warning that the car should still start?

[osx]

You will have to connect the diagnostic when the car manages to start. You can run it with the engine running just to get the saved error codes.

[davidm3836]

This is a bit random for a Sunday morning but hopefully someone can help. Is there anyone in their infinite wisdom that is able to tell me which wire is the signal wire/wake up wire that goes from the BSM to the engine ECU and if so which wire on which connectors? I have had a look at some wiring diagrams but can't make any sense of it. Thanks 2009 C5 2.0 diesel. I can provide VIN if required.

[GiveMeABreak]

The communications between the BSI and the engine ECU are mostly via the CAN data networks, so not sure what it is you are trying to ascertain. Wiring diagrams are specific to each vehicle.

If you want the injection Diagram, then put up your VIN for me (please post your VIN in full without spaces - it will be automatically masked from public view after submitting your post & will only be visible to staff).

[davidm3836]

Hi thanks for the reply, I still have the same braking system faulty message as before and after watching endless videos and endless reading I am trying to see whether or not the engine should still start. Seemingly it should still start even with that warning present? I have seen a video that shows 1 broken wire (seemingly a signal wire) which was a 12v supply to the ecu meant the car wouldn't start. Just trying to find everything I can. Do I post private the VIN or on here? Thanks again

[GiveMeABreak]

Post it here - see my last comment about the VIN.

It's not going to be helpful without a diagnostic code, so I'd either check your VCI is not broken or see if you can get somebody else with a kit to run a diagnostic.. There shouldn't be anything that is preventing you talking to the BSI to check for faults.

[davidm3836]

Ok thanks, the VIN is VF7**************[VIN obfuscated, can be read by forum staff]

[GiveMeABreak]

Here you go:



1320 is the Engine ECU
Wire 7842J: remote control wake-up information

Most of the component hardware codes are on the Wiki in sections here:

https://frenchcarforum.co.uk/wiki/Elect ... ring_Codes

[davidm3836]

Hi there, thanks for the reply with all that data. I am not the best at understanding the diagram so wonder if you are able to answer a couple of things? Where you said the wire is 7842J, is that code printed on the wire itself and the small block with the numbers inside , are they referencing the PIN numbers in a connector block? Sorry I know im probably sounding a bit daft but just looking for some clarity. Many thanks

[davidm3836]

Hi there, apologies for bringing this thread back to life but im wondering if anyone can list a wiring diagram for the ESP system in the cart? Many thanks

[GiveMeABreak]

Hi there, thanks for the reply with all that data. I am not the best at understanding the diagram so wonder if you are able to answer a couple of things? Where you said the wire is 7842J, is that code printed on the wire itself and the small block with the numbers inside , are they referencing the PIN numbers in a connector block? Sorry I know im probably sounding a bit daft but just looking for some clarity. Many thanks

Yes and yes.
I'll put the ESP system up for your shortly.

[GiveMeABreak]

Here you are:

[davidm3836]

Marc, thanks so much, might just get this problem solved before I have to hand it over to an auto electrician, which is the last resort.