OBD-II Generic Error Code P0055: How to Fix It

Q: What does error code P0055 mean?

P0055 means the engine control module (ECM) has detected abnormally high or low resistance in the heater circuit of the downstream oxygen sensor (HO2S) on Bank 1, Sensor 3. This indicates a problem with the sensor's heating element or its wiring.

Q: Can I drive with a P0055 code?

Yes, but it may cause poor fuel economy and increased emissions. Your vehicle may fail an emissions test. It's best to fix the issue promptly to avoid further problems.

Q: How do I know which oxygen sensor is Bank 1 Sensor 3?

Bank 1 refers to the side of the engine containing cylinder #1. Sensor 3 is the third oxygen sensor in that bank, typically located after the catalytic converter (downstream). Consult your vehicle's repair manual or look for a sensor behind the catalytic converter on the exhaust pipe.

Q: Will a bad oxygen sensor cause the check engine light to flash?

A flashing check engine light typically indicates a severe misfire, not an oxygen sensor issue. P0055 usually causes a steady check engine light. If your light is flashing, address the misfire first.

Q: How much does it cost to fix P0055?

If you DIY, an oxygen sensor costs $20-$100 and tools are minimal. If a mechanic does it, expect $100-$300 depending on labor rates and parts.

Abstract

Error code P0055 indicates a problem with the heater resistance in the downstream oxygen sensor (HO2S) of Bank 1, Sensor 3. This sensor monitors the catalytic converter's efficiency and helps the engine control module (ECM) adjust the air-fuel mixture. A faulty heater circuit can cause poor fuel economy, failed emissions tests, and increased emissions. This guide will help you diagnose and fix the issue.