Electrical faults after D4 3.0 body R&R

The mechanics gave-up in favour of my son and I seeing what we can do.

The HS canbus end to end integrity is OK by a resistance check so now concentrating on ecm power and grounds. The brake switch was reset in case it had been upset but still not starting, noting that the brake pedal is very high and hard. The switching off when attempting to start could just be switching off in the absence of the OK brake fluid pressure signal from ABS because the canbus is inoperative, so that issue is being ignored for the moment. However brake switch operation is still to be checked using the IIDtool.

The ABS module doesn't feature in the list of ecus. Power is at the FL & fuses which are OK.

I'd expect it has already been checked, but sometimes the simple things...

Is the battery ok and is the brake pedal being stepped on hard enough to set the brake switch now that there is no vacuum assist?

Yes, I'm looking/hoping for something simple. However battery voltage is fine and the brake switch was R&R'd to reset it. Upon wanting to check the switch status using the IIDtool in case the pedal is too hard to press down enough, there was no sign of the ABS module then again no sign for ecu s/w level status. I had earlier noticed that the HDC switch didn't provoke any response. The diagnostic port K line goes to the ABS module so if the ABS module is functioning then I would expect the ABS module would have comms faults for the other modules which are reporting comms faults with the ABS module, but there aren't any.
Next check is for power and ground at the ABS connector.

I'm still pondering why the suspension raise and lower switches are both reported as on, which means that the voltage on both those signal wires is below the threshold for being considered off. The 2 wires connect to the suspension ecu via different plugs but presumably run in the same harness until close to the suspension ecu.

The 2 ABS connector ground pins continuity between each other but OC to body - almost there I feel.

Power and ign OK.

The nut from the earth stud was missing. The mechanic had disconnected the winch earth cable from the stud leaving the other terminals unclamped. Now no coms faults although it didn't start with only just the aux battery which is getting low. Might still be something else to be resolved.

Quote:

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Originally Posted by Graeme

The nut from the earth stud was missing. The mechanic had disconnected the winch earth cable from the stud leaving the other terminals unclamped. Now no coms faults although it didn't start with only just the aux battery which is getting low. Might still be something else to be resolved.

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Always the most frustratingly simple thing as usual. Well done

Now to get the power steering pump to work and to sort out why the suspension raise and lower switches don't work. I thought that maybe the reservoir's filter was blocked so ordered a new reservoir, only to discover that the filter looks spotless with most of the fluid having been removed. I'm now wondering if the mechanic or his apprentice left a cloth plug in the pump inlet as the pump seems to be cavitating with no fluild being returned to the reservoir.

Graeme, eventually a simple, if partial, solution. Earths, eh? Who'd have thought?

Well played.

Pete

Another issue resolved. Suspension system diagnostics showed just over 1V on the main 12V supply. The 20A fuse was missing. I had wondered from where the 20A fuse in the console had come so now I knew, but I had forgotten that it was I who had removed the fuse to prevent any further possible lowering whilst on the trailer to the mechanics.
1 issue to go...