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2003 Honda CR-V P1166 O2 Sensor Code: Causes, Diagnosis & Fixes

Model: 03 Honda CRV Fault Code: P1166 Posted: 2008-05-07 18:51

Hello, I own a 2003 Honda CR-V with 68,000 miles. I recently received a diagnostic code P1166 from my OBD-II scanner. The code indicates an issue with the front oxygen (O2) sensor circuit. When I disconnect the battery, the code clears immediately. However, when I turn the key on and start the engine, the check engine light comes on within seconds. I'm wondering what components or systems to inspect first. Is this a sensor failure, wiring issue, or something else? Any advice would be greatly appreciated. Thanks, Jim

Related fault codes

P1166

Comments (3)

Anonymous 2008-05-08 07:49

P1166 is a Honda-specific code related to the front oxygen sensor circuit. While it may point to an O2 sensor failure, it could also indicate wiring or connector issues. If you're comfortable working on your vehicle, start by replacing the front O2 sensor. This is a common fix for this code. Always check for corrosion, loose connections, or damaged wiring before assuming a faulty sensor.

Anonymous 2009-01-15 13:24

Hi, I have a 2003 Honda CR-V EX with the P1166 code detected using an Acton CP9125 OBD-II scanner. The issue is listed as: Oxygen Sensor (Air/Fuel Ratio) - Front. I purchased a Denso part #234-9005 from Amazon and borrowed an O2 sensor socket from AutoZone. First, I disconnected the connectors—one required unscrewing the clamp for easier access to the plastic plug. Then, using the socket, I removed the old sensor; it was slightly tight but came out easily. The tip of the sensor was black, indicating possible contamination. I hand-tightened the new sensor into place and then used the socket to secure it properly. After reattaching the connector and tightening the clamp, I completed the installation in about 15 minutes. I cleared the code using the OBD-II scanner and restarted the engine. The scan showed zero codes. Thanks for the help! Darryl

Anonymous 2009-01-15 14:31

Thanks, I was initially thinking it might be a faulty oxygen sensor—those components are known to be durable but can degrade over time. The check engine light has been on since last year, and my fuel mileage hasn’t changed at all, which suggests the issue may not be affecting performance. Since I don't need to pass emissions tests in my state, I’ll monitor it closely for now. Does anyone know if oxygen sensors can be cleaned or regenerated instead of replaced? Thanks again for the insight! Jim