P420 and P1456 Error Codes - 2002 Honda CR-V (204,500 Miles) | OBD2 Diagnosis & Solutions
My 2002 Honda CR-V has returned with P420 and P1456 error codes at 204,500 miles. The vehicle previously had its catalytic converter and downstream oxygen sensor replaced 18 months ago, around 180,000 miles. After that service, the check engine light remained off until last week when it came back on. I have already replaced the front O2 sensor and gas cap, cleared the codes, and the light stayed off for several days. However, today after filling up and installing the new gas cap (tight), the check engine light reappeared within 5 miles of driving. I have not performed an OBD2 live data scan yet, as my scanner does not support real-time readings. Given that both P420 and P1456 are related to exhaust system performance and catalytic converter function, I suspect either a recurring issue with the converter or underlying engine parameter misalignment. Could the original manufacturer's recommended replacement part have been used? Any advice on diagnosing these codes specifically in a 2002 Honda CR-V would be greatly appreciated.
Can you confirm whether both P420 and P1456 appeared simultaneously when the check engine light returned? Does your OBD2 scanner provide live data for fuel trims and oxygen sensor readings? This is important because if the catalytic converter is failing again after 18 months, it may indicate that engine parameters (like fuel trim) are out of specification. Always ensure you used the OEM-recommended part during replacement. Check official Honda service documentation or forums for detailed troubleshooting on P420 and P1456 codes in 2002 CR-V models. Also inspect the exhaust system for leaks near the replaced catalytic converter, as even small leaks can trigger these codes.