P0030: O2 Sensor Heater Control Circuit — Bank 1 Sensor 1
What to do
The car will drive normally and you may notice nothing at all. It will fail an emissions test, and fuel economy suffers slightly on short journeys. Book it in without urgency.
What this code means
An oxygen sensor only reads accurately once it is hot, so each one carries its own heater to bring it up to temperature within seconds of a cold start rather than waiting for the exhaust to do it. This code reports an electrical fault in the heater circuit for the upstream sensor on bank 1. The sensor's oxygen reading may still be perfectly good once the engine warms — what is lost is the closed-loop fuelling during the first minute, which is exactly when most emissions are produced.
Likely causes
Start here
Less common
- Open circuit in heater wiring · moderate
- Exhaust heat damage to sensor harness · moderate
Rare
- Control module driver failure · specialist
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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