Citroen XM Forum

XMdownunder wrote: ↑

Tue Jan 16, 2024 9:37 am

I had a beaut new issue pop up today during short drive the hydraulic pressure, stop command, coolant level and engine oil pressure warnings lit up together. It was a hot day of about 30 degrees C and I pulled over check fluid levels all OK gave 10 minutes cool down and when restarted the lamps stayed off. But the same lamps came on again at end of the short trip home.

Assuming the engine idle didn't drop to a level where it was nearly stalling, this looks like an instrument cluster fault.

All those lamps operate from a single +12v supply and each one is shunted to Gnd to illuminate the lamp.
The Gnd links are connected together through diodes, so a single trigger can turn on a pair of lamps, such as the warning lamp and the STOP lamp, but each feed in is separate.

Possibly one of the circuits triggered and there is a current leakage on the circuit allowing all the lamps to be brought on together.

Power up the instruments cluster and individually shunt each of inputs of the respective circuits to Gnd. Each should bring on that lamp and the STOP lamp, but one, or more of them are bringing on the whole lot.

Hydraulic level and Hydraulic pressure. Black 15 pin connector, Pin 4.
Coolant temperature Black 15 pin connector, Pin 2.
Coolant level. Yellow 15 pin connector, Pin 8.
Engine oil pressure sensor. Yellow 15 pin connector, Pin 7.

My first guess would be the coolant temperature, or level sensor as they can be a bit flakey mainly due to contamination of the probes.
Maybe the engine did get a bit warm...is the fan operating?

It could be the circuit board is misplaced so light leakage from the STOP lamp leaks into the other lamp housings.

See Gabor's excellent circuit diagrams in the linked thread.
viewtopic.php?f=13&t=7592&start=110

Thanks DM I was panicked a bit knowing my spheres are below par and concerned I had real hydraulic failure but hoping it was a transient electrical fault. I will run the circuit tests as suggested but not rule out hydraulic failure and will order a new set of spheres from France. It got weirder last night drove the XM home parked in garage under house no warning lamps lit turned off ignition and came inside. Shortly afterwards SWMBO calls out that my XM alarm is going off she could hear the hydraulic pressure alarm through the floor, I rushed down to garage but all quiet nothing unusual. Is it possible my XM has got AI and self activated its sense of humour module?

In 2024 anything's possible.