Berlingo Fuel Filter Heater Error

I had a similar problem with my old Vauxhall Astra, although it was a petrol engine. Error codes pointing to seemingly unrelated sensors, poor performance, and a general feeling that the car wasn't running right. Turned out to be a dodgy connection in the wiring harness. Have you checked the cable and plug connection to the fuel filter heater itself? A defective connection there could cause all sorts of havoc.

Thanks! My electrical knowledge is limited. What should I look for when checking the cable and plug connection? Just ensuring they're secure, or more? Should I check voltage/resistance with a multimeter, or can I visually inspect? What should I look for?

Visual inspection first. Look for corroded pins, cracked or brittle wiring, anything out of the ordinary. Give the wires a gentle tug to see if any are loose. If everything looks okay visually, then yes, a multimeter would be the next step, but that requires some knowledge of what readings you should be getting. Honestly, given your description, it might be best to take it to a workshop. They'll be able to diagnose the issue properly and repair or replace the wiring if necessary.

The mechanic inspected the wiring and connections to the fuel filter heater, and it was a corroded connector. They cleaned and repaired the connection, and everything is running smoothly again. The total repair cost was 95€.