i20 Oxygen Sensor Heater Error

Interesting situation. Did you check the voltage at the connector itself? I recall a similar issue with a 2018 Opel Astra, where the wiring appeared perfect, but corrosion within the connector was causing intermittent connection problems. The symptoms were comparable: check engine light, increased fuel consumption, and error codes pointing towards the oxygen sensor. Have you attempted any sensor testing, such as checking the resistance of the heater circuit?

Thanks for the input! I haven't checked the voltage at the connector yet, I'll add that to the list. When you mention corrosion inside the connector, was it visible, or was it hidden? Also, what was the eventual repair with your Opel?

In the Astra's case, the corrosion was not immediately apparent upon visual inspection. Only after closer scrutiny, and some electrical testing, did we discover the issue. The repair involved replacing the corroded connector and a section of the wiring harness, as the corrosion had spread a bit. Given your mileage and the symptoms you're describing, I'd strongly suggest a thorough inspection of the connector and wiring. If that doesn't reveal anything, it might be prudent to consult with a qualified workshop for a more in-depth diagnosis of the exhaust system.

Appreciate the insight! I finally checked the voltage and you were spot on. The cable or plug connection was defective. After replacing the cable, the error disappeared, the check engine light turned off, and the fuel consumption is back to normal. The repair cost 95€.