You need the extension leads on the multimeter test ports. They're very useful when testing longer wires. On the other hand multiecuscan (mes) diagnostics would be able to show canbus errors which are not accessible by general obd tools.

It may very well be related to the door wiring inside the rubber sleeve or it's bcm failure which would be very expensive and not worth fixing.

Finding each pin on the connectors is another chore, usually pins are numbered inside the connectors.

RalphM said:

There is a post on here with the same problem it was water getting in the fuse box,
maybe it's worth having a good look there for any damp corrosion and so on.

https://www.fiatforum.com/grande-punto/299503-engine-wont-turn-off-wet-engine.html

https://www.fiatforum.com/grande-punto/323880-grande-punto-wont-turn-off-key.html

Click to expand...

Thanks. I've had the fusebox out of the car, it was as dry as a bone and no corrosion. The car has been garaged throughout the pandemic so it hasn't seen any rain for 20 months!

That being said, I could conduct a more extensive investigation and check every single contact, fuse and relay.

eeeno said:

You need the extension leads on the multimeter test ports. They're very useful when testing longer wires. On the other hand multiecuscan (mes) diagnostics would be able to show canbus errors which are not accessible by general obd tools.

It may very well be related to the door wiring inside the rubber sleeve or it's bcm failure which would be very expensive and not worth fixing.

Finding each pin on the connectors is another chore, usually pins are numbered inside the connectors.

Click to expand...

Mmm, I'll need to acquire some extension leads as the multi-meter leads are obviously short and won't span the width of the car.

My OBD tool shows no pending or historic faults but 1 logged fault. Code is U1706. No warning lights appear on the instrument cluster.

https://www.fiatforum.com/stilo/244982-u1706-can-brake-control-node-1-9-jtd-2.html

According to this thread, this code is a CAN network fault relating to comms between the ECU and ABS. Although my symptoms are different, the OP did go on to locate a fault in the ABS wiring loom, however his car is a Stilo so set-up may be different. I guess it doesn't hurt to check this wiring too.