Electrical Gremlin - 02 Volvo V70 XC

theherbfarmer · Post by **theherbfarmer** » 19 Jul 2025, 17:35

Hey Gang,

I’m trying to chase down an electrical gremlin. Had all the tell tale signs that my CEM was bad due to CAN bus issues; dash would light up, brake failure light, and loud transmission clunks. Sent in my CEM to Volvo Diagnostics in the UK to get transferred and swapped out. Got it back, and I would still get the same issues but this time the transmission clunks went away and the dim cluster would turn off but the check engine light would stay on. I figured maybe it was the 2 main 50a relays on the board. Replaced those and still have the issue. I ordered a couple of more to replace the ECU relay under the hood. Does anyone know what it could be?

Post by **DavidE7** » 20 Jul 2025, 20:10

I think the yellow stripe relay may be incorrect. Try downloading the Volvo Electronic Wiring Diagram (EWD) pdf book and read the page for the CEM relays.

I would also recommend finding a "pick-n-pull" junkyard with any P2 Volvo (S60, S80, V70, XC70) and getting a bunch of spare relays and fuses. They are very useful for quick testing.

Post by **jonesg** » 20 Jul 2025, 22:32

what are the codes it shows ?