2003-2005 Honda Civic Hybrid ULEV vehicles
Research the vehicle manufactures service bulletins along with following the diagnostic procedure before replacing parts is imperative to have a successful repair.
On certain 2003-2005 Honda Civic models, if your check engine light comes on due to a catalyst efficiency trouble code (P1420 or P2000), call your Honda dealer to verify TSB 11-043 has been completed before you proceed to diagnosis these trouble codes. This TSB requires a PCM reprogram to improve accuracy of the catalyst detection system. Do not replace any oxygen sensors until this service bulletin has been followed.
After all required test procedures have been followed you may be led to replace the catalytic converter and oxygen sensors. Even though you may suspect one sensor to be at fault you may be required to replace them in pairs. It is not common to replace oxygen sensors in pairs but in some situations, it may be necessary due to the tight monitoring condition by the engine computer system on exhaust emissions. Certain performance levels are required from the sensor input to ensure the oxygen sensors are working together correctly. Honda technical service bulletin TSB 11-043 will provide the needed information concerning this situation in detail.
To verify if your application will require the computer relearn and/or oxygen sensor replacement, refer to the service manual for your vehicle application, or call the GoTech technical support team at 1-855-207-5630 M-F 7:30-6:00 CST for assistance.