Transit Knock Sensor Wiring

I had similar issues with my Transit. Rough idling, check engine light – the works. A knock sensor tells the engine control unit (ECU) if the engine is 'knocking' or 'pinging', which is premature combustion of the air/fuel mixture. It protects the engine from damage. Have you checked the wiring harness thoroughly? Those things can corrode or get damaged pretty easily. Is the wiring properly shielded? Sometimes, electromagnetic interference can cause false readings.

Good shout! I suspected the wiring. When you say "wiring harness", are we talking about the entire bundle, or is there a specific section I should be focusing on? Also, how sensitive are these sensors, really? Could a slightly loose connection throw the whole system off?

By wiring harness, I mean the specific bundle of wires going to the knock sensor itself. They are pretty sensitive. Even a slightly corroded or loose connection can cause problems. If you've checked the connections and wiring and still have problems, it might be worth getting it checked out by a workshop.

Thanks a bunch for the advice! You were spot on about the wiring. Took it to my local mechanic, and it turned out to be a corroded connector on the knock sensor wiring. They cleaned it up and replaced the connector. Cost me 95€ all in. Check engine light is gone, and it's running smooth as butter. Fuel consumption is back to normal too! Appreciate the help!