OBD-II Generic Error Code P0042: How to Fix It

Q: What does error code P0042 mean?

P0042 means the heater circuit for oxygen sensor Bank 1 Sensor 3 (downstream) has failed. This sensor helps monitor catalytic converter efficiency and the heater helps it reach operating temperature quickly.

Q: Can I drive with a P0042 code?

Yes, but you may notice reduced fuel economy and increased emissions. Over time, it can damage the catalytic converter. It's best to fix it promptly.

Q: Where is Bank 1 Sensor 3 located?

Bank 1 refers to the cylinder bank that contains cylinder #1. Sensor 3 is the second downstream sensor after the catalytic converter. Typically, it's threaded into the exhaust pipe behind the converter.

Q: How much does it cost to fix P0042?

DIY cost is about $30-$80 for an O2 sensor. A mechanic will charge $150-$300 total including parts and labor.

Q: What tools do I need to replace an O2 sensor?

You'll need an O2 sensor socket, ratchet, extension, digital multimeter, and OBD2 scanner. Optionally, a breaker bar for stubborn sensors.

Abstract

Error code P0042 indicates a problem with the heater control circuit of the oxygen (O2) sensor located in Bank 1 Sensor 3 (downstream). This can cause increased emissions and reduced fuel economy. The fix typically involves testing the sensor's heater circuit and replacing the sensor if faulty.