CANBUS Questions

[Citroënbender]

I’m still battling with the naughty Pug 307.

Among the faults it throws somewhat at random, is a complete loss of (electric) steering assist. Highly dangerous when you’re entering a small roundabout at 45km/h.

I’m trying to work out if the fault lies in another module as the transmission logs an intermittent fault for loss of CANBUS signal.

If I physically unpick the two bus pins from the steering module connector on the harness and insulate them out of the way, everything else on the bus (eg brakes, dash cluster) should still work pretty much as normal, right? I don’t believe it’s a terminating node. Hence this particular question.

Troubleshooting the steering is a bit difficult because I don’t have a pinout for the connector or access to its parameters. So I want to see if it has an inbuilt limp mode for no CAN data or if it defaults to no assist immediately.

[russellw]

What is the DTC it throws becasue I can probably get you diagnostic subroutines for the DTC given the global PCED applies across all OBD2 compliant systems.
I can probably dig up the pinout for the EPAS connector if you give me the year of the 307.

[Citroënbender]

It’s a 2004 model 307, the EPAS has a two pin power plug for the pump, and a nine pin socket but I think only five are populated on the harness - presumably 2x CAN, +12V, GND and a diagnostic line. I’ve got cracked software that is pretty good for the most part but it doesn’t have any dialogue with the module, even if I try diagnosing as another model.

Normally when the EPAS fails on these, it’s due to internal leakage and the multi pin connector drips with fluid. This one is decisively dry.

These are the only screenshots I’ve saved. There’s a sticky (petrol) EGR which gives me permanent faults - easy to fix, just need a round tuit - and intermittent failure mode on both transmission (default to full hydraulic) and EPAS. I swapped TCMs (they’re external and not hard coded) with no change.

I’m not sure how the fault code of “87” crosses over to universal codes.

Also I’m suspicious of the way this fault is reported, I’d have thought a loss of brake module data would show up as a VDC fault or loss of speedo but it never does.

There’s one post on MHHAuto with a matching fault, but no clear resolution (only advice was to clean the ABS connector, true for damp climates), and the OP doesn’t say if he had steering issues. So I can’t say if my steering problem is simply happening because it’s downstream of another fault, or is a self-contained failure.

[russellw]

From what I have available the 87 faulty code relates to the vehicle speed input from the ABS module on the CANBUS has no signal.
I'd suspect this could be an ABS wheel speed sensor intermittent fault or something else in the ABS system.

[Dr Smith]

This is all above my head but it was interesting reading both issues and possible solutions.

[ozpacman]

Originally Posted by Dr Smith

This is all above my head but it was interesting reading both issues and possible solutions.

I thought it must have been a couple of blokes from Mozambique having a yarn in their native Swahili!

[Dr Smith]

Originally Posted by ozpacman

I thought it must have been a couple of blokes from Mozambique having a yarn in their native Swahili!