S80 diesel preheating lamp issue

Alright, Volvo gurus, I'm at my wit's end! My 2007 Volvo S80 diesel is throwing a tantrum. The preheating lamp refuses to switch off, the check engine light is mocking me, and it's puffing out smoke like a dragon when I hit the accelerator. It's got 243795 km on the clock. I'm thinking it's the preheating control unit playing up – maybe a dodgy cable or plug? Anyone seen this before? It's like the car's trying to be a steam train!

4 comment(s)

Sounds like an electrical fault. Is it possible to read out the error codes? It might point directly to the preheating control unit or a related component in the ignition system.

Yeah, I had a peek at the error codes, and it's definitely flagging the preheating control unit. But could a faulty unit really cause all those symptoms – the light, the engine light AND the smoke? Or is it more likely a cascading failure of some sort?

A defective control unit can definitely trigger all those symptoms. The smoke likely indicates unburnt fuel due to incorrect preheating. If the error codes pinpoint the unit, it's highly probable that's the culprit. Getting it checked by a workshop is the most sensible thing to do.

Thanks a bunch for the advice! It turned out to be exactly what you said: the preheating control unit. Replaced it, and she's purring like a kitten again. Cost me about 95€ for the part and labour. Cheers!

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