Electrical faults after D4 3.0 body R&R

[Graeme]

Lots of HS canbus faults suggesting OC somewhere, with wiring from ECM to TCCM/TCM/ABS still to be fully checked. TCM has 2 copies of HS canbus with 1 pair open circuit somewhere, have yet to recheck continuity from ECM connector to TCM connector once the D4 comes back to my place but bridging the 2 canbus circuits didn't change anything. Instrument cluster doesn't operate if the TCCM is unplugged. ECM connector that has the HS canbus wires was not disturbed in the body R&R, only the other ECM connector (engine harness) unplugged to stay with the engine. No bent pins in the ECM socket. Diagnostic socket has direct connections to the ECM and TCM so doesn't require access via the HS canbus to retrieve comms faults from those modules.

Engine has run twice sounding good, topped-up coolant and general checking but wouldn't restart until left for a few hours but now won't restart. Instrument cluster powers-off when attempting to start but no noise from the starter motor solenoid. Suspect a ground issue but mechanic rechecked body to engine cable. A detailed check will commence once the vehicle is back with me.

Looking for suggestions as to what may have been left disconnected or anything simple to be checked before getting into the detailed checking.
Thanks.

NB The original engine harness was fitted to the replacement engine before the body was refitted.

[DiscoJeffster]

About the only thing I can add is the rear large connector is known to be an issue and I recall pins can get pushed out when reconnecting. Some past canbus issues have been resolved there. Good luck. I hate troubleshooting those types of issues.

[Graeme]

Are you referring to the ECM connector that has to be unplugged?

[DiscoJeffster]

Are you referring to the ECM connector that has to be unplugged?

At the rear of the vehicle (LHS, near the left hand bag I recall, on the frame) is a large multi-pin connector. There have been posts prior where this connector has been an issue for body off.

[Graeme]

Thanks lots. Might have to see if the car is still on the hoist in the morning.
I'll see if I can find it in the wiring diagram.

[Graeme]

The park brake module contains the HS canbus far end terminating resistor. If that connector hasn't been fitted than comms faults will occur even if some data can get through. A definite contender!

[Graeme]

The connector had been fitted but this morning R&R'd to check pins and reseat, but no change.
Gbox harness has solder joints for the 2 sets of HS canbus so the body side connector only has to supply 1 side although wiring diagram shows both from ECM via different solder joints, so more ECM to gbox plug is required.

[Pierre]

Graeme, many find that the two connectors on the rear left hand rail randomly break conductors, so worth a check. The plug on the EPB loom is also a candidate for that behaviour. We are just troubleshooting our 08 RRS with the same sorts of issues, one of which was a self-bricked TCCM!!

Good luck with troubleshoot. I am watching with interest.

Pete

[Graeme]

Thanks Pete for your suggestions.

The workshop owner today returned from holidays. The mechanic has asked to keep the car 1 more day, presumably to work through with the workshop owner who most likely wouldn't be wanting to return the car not running.
I'll give that connection a thorough check if the faults are unresolved, after first checking the resistance between the 2 bus wires to ascertain if the bus is intact or not.

The TCCM from my L322, an identical part but might have different software, was tried last Thursday with no improvement.

[Airmech953]

I had similar problems on my 05 Disco. The fault was eventually traced to a crushed canbus wire at the rear nearside connector (behind the wheel). Continuity checks were ok but when the individual wires were given a shake test, then the faults could be replicated. A new 6 inch length of canbus wire and connector pin fixed the problem for me.