ESP ECU communication fault

[dackjaniels]

Hi,

307 2.0 HDI, last 8 chars of vin are 82375805.

I have a recurring fault that is putting the car into limp mode.
It relates to communication between the ESP ECU and the Engine ECU (either no communication or more frequently it shows incorrect value received).
When I scan with PP the ESP ECU, more often than not, cannot be read during the global test (some message about ECU not referenced, sorry not sure exact wording right now). I can however read the faults by clicking on the ECU in the global test list and confirming a warning message.

Sometimes it all works faultlessly though that is becoming more rare as each day passes. If I get a good read and clear the faults it always comes back at some random point during my next 10mile+ journey and straight into limp mode.

It seems to me like a dodgy wire somewhere but I have yet to find it. This is where I could do with some help. I have a multimeter but need a little help determing where to use it :-)

The ESP ECU is the Bosch 5.7 and as such it appears it is one unit with the ABS ECU which I believe is attached to the front of the hydraulic block in front of the passenger side front wheel. I've checked the connections here visually and saw no signs of corrosion or water ingress. There is also a much smaller connector on the rear of the unit which I left for now as I couldn't get it off and didn't want to snap it. Any ideas how to remove this one without damaging it?

I also checked the connecters where the wiring looms connect just in front of the fuses in the under the bonnet fuse box and they all look clean and dry.

What should I do next? It seems to me the ESP ECU connects to pins 2 and 4 of the BSI. It also seems that the engine ECU connects to pins 2 and 4 of the BSI. If I'm reading the diagram correctly (and this is where I really need advice) the two wires from the engine ECU at some point are crimped with the two wires from the ESP ECU and then two wires (as opposed to 4) lead to the BSI pins 2 and 4.

I've attached diagrams from Peugeot Sedre and would appreciate any help from someone who can read these diagrams correctly.

I want to know what I should do next in my efforts to track down what I assume is a loose connection.

Much appreciated!
Steve

EDIT: It appears my attached screenshots are hopelessly small yet I've seen other posts with normal size pics. If someone can tell me how to upload full size ones I will do so EDIT2: Nevermind, pics sorted.

[danthevan]

From reading on here, most esp problems seem to be down to the brake pedal switch, so may be worth changing that for the few quid it costs and see what you get

[dackjaniels]

Thanks danthevan, I'll check out the switch. Not sure it would cause the communication fault I'm experiencing but will definitely check it operates correctly.

Anyone any idea where the crimps (E900 and E901) are physically located in the car/wiring loom? I wonder if this may be a weak point.

[matt268uk]

Just to let you know ,you uploaded your pics fine,when users click the thumbnail it grows and becomes clear,no problems at all to read the diagrams.

[dackjaniels]

Originally Posted by matt268uk

Just to let you know ,you uploaded your pics fine,when users click the thumbnail it grows and becomes clear,no problems at all to read the diagrams.

Yeah they are fine now thanks Matt.

The problem at first is I uploaded them as PNGs and when I did so they seemed to obey the file size and dimension restrictions I was seeing listed in the attachment window. Uploading them as JPGs has solved the problem (they were about 3 inches wide on the first attempt and totally unreadable!)

Steve