Citan oxygen sensor heater failure

My 2017 Mercedes Citan with a diesel engine is throwing a fit. The check engine light is on, and the error memory says there's an oxygen sensor heater failure. I've noticed my fuel consumption is up too, after only about 14505 km. I suspect a faulty sensor in the exhaust system but I was wondering if anybody has any experience with this? I've checked the oxygen sensor cable and plug - nothing obvious. Is there a way of sensor testing without special tools?

4 comment(s)

Oxygen sensor heater failures are common. Did you check the heater element resistance? A multimeter should do the trick. Often it’s the downstream oxygen sensor that throws this code. Have you checked that one?

Thanks for the quick reply! How do I find the correct resistance value? I dont want to mess anything up. And how do I know which one is the downstream oxygen sensor?

The resistance value should be in the service manual for your Citan. If you don't have one, a quick web search for 'Mercedes Citan oxygen sensor resistance' might help. The downstream oxygen sensor is after the catalytic converter. If you're not comfortable with sensor testing and finding the correct values, it might be best to visit a workshop.

Thanks! I think you are right. I will take it to the workshop. I called them and they said they will do sensor testing. They quoted around 95€, so hopefully its just a defective cable or plug connection.

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