P0171 and P0420 Fault Codes on 2004 Honda Accord LX 4-Cylinder
I own a 2004 Honda Accord LX with a 4-cylinder engine. A few days ago, the check engine light came on during an extremely cold day, with temperatures reaching -33°F. Since then, even as ambient temperatures have improved, the check engine light remains illuminated. I've attempted to clear the fault codes using an OBD-II scanner, but they return shortly after. The presence of both P0171 and P0420 codes is concerning, and I'm seeking advice on how to diagnose and resolve these issues effectively.
First, address the P0171 code. Refer to OBD-Codes.com for detailed information on P0171: http://www.obd-codes.com/p0171. Once you've resolved the underlying issue, clear the codes and complete a drive cycle to see if the problem persists. If the P042-0 code remains, further diagnostics are needed—this may indicate exhaust system inefficiency or catalytic converter failure.