martin_nacht98

V40 preheating lamp and check engine light

Hi, I've got a 2012 Volvo V40 diesel with 217382 km that's throwing up some weird errors. The preheating lamp isn't switching off, and the check engine light is now constantly on. I've also noticed some smoke when accelerating, which definitely wasn't there before. I suspect the preheating control unit might be defective. After some digging, it seems like a likely cause could be a defective cable or plug connection to that component. Anyone experienced anything similar?

A 2012 Volvo V40 diesel is experiencing issues with the preheating lamp not switching off and the check engine light remaining on, accompanied by smoke during acceleration. The suspected cause is a defective preheating control unit, potentially due to a faulty cable or plug connection. A similar issue in another vehicle was resolved by checking and replacing a connector that was not receiving the correct voltage. It is suggested to inspect the connector for damage or corrosion and consider professional diagnosis to avoid further complications.

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4 comment(s)

That sounds frustrating! I had a comparable issue with my old Opel Astra a few years back. Same symptoms more or less: persistent preheating light, check engine light, and even some rough idling. Did you check the voltage at the preheating control unit connector? That's where my problem started, because it was not getting the correct voltage, I changed the connector.

Thanks for the quick response! I haven't checked the voltage at the connector yet, but that's a good shout. Where exactly was the defective connector located in your Astra? Was it visibly corroded or damaged?

On my Astra, the connector was right next to the engine block, so it was exposed to a lot of heat and vibration. It wasn't visibly corroded at first glance, but after unplugging it, I noticed some damaged pins inside. Given your symptoms and the potential for electrical issues, it might be best to get it properly diagnosed at a workshop. Could save you a lot of time and hassle.

Thanks for the advice. I'll check the connector, but I think you're right, I'll probably take it to the workshop. The cable was indeed defective and the repair cost 95€. Appreciate the help!

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VOLVO

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V40