P2239 Mercury Code - O2 Sensor Positive Current Control Circuit High Bank 1 Sensor 1

P2239 indicates an issue with the O2 Sensor Positive Current Control Circuit High for Bank 1 Sensor 1, meaning the sensor's measured current is higher than expected.

Symptoms may include an illuminated Check Engine Light, reduced fuel efficiency, rough idling, or poor engine performance.

Common causes include a faulty oxygen sensor, damaged wiring or connectors in the O2 sensor circuit, or a malfunctioning engine control module (ECM).

Start by using an OBDII scanner to confirm the code, inspecting the O2 sensor and its wiring for damage, and testing the sensor's circuit for proper voltage and current.

While the car may still run, driving with this code can lead to poor fuel economy, increased emissions, and potential long-term damage to the catalytic converter.

Repairs may include replacing the faulty O2 sensor, repairing or replacing damaged wiring or connectors, or reprogramming or replacing the ECM if necessary.

A dirty air filter is unlikely to cause this code directly, but it can contribute to poor engine performance, which may exacerbate sensor issues.

The cost depends on the cause, but replacing an oxygen sensor typically costs $150–$400, including parts and labor.

While it's rare, a failing catalytic converter can indirectly affect O2 sensor readings, potentially contributing to this code.

If you're experienced with car repairs and have the necessary tools, you might be able to fix it yourself. Otherwise, a professional mechanic is recommended for accurate diagnosis and repair.