2005 Hyundai Elantra GT P0130 and P0501 Codes: Diagnosis and Fixes for O2 Sensor and Speed Sensor Issues
I own a 2005 Hyundai Elantra GT with a manual transmission. My car has been throwing multiple diagnostic trouble codes, including misfire, oxygen sensor issues (O2 Sensor 1 and 2), system lean, and system rich conditions. After extensive research, I concluded that the Engine Control Module (ECM) might be faulty. I replaced it with a used ECM from another 2005 Elantra (same model year and engine type), as vehicles from 2001 to 2006 share compatible ECMs. This change reduced the number of codes from nine down to two: P0130 (Oxygen Sensor 1 Circuit Malfunction) and P0501 (Vehicle Speed Sensor Circuit Range/Performance). I replaced both O2 sensors about a year ago, so I believe they are not the root cause. The speed sensor was also replaced, but the P0501 code persists. What could be causing this ongoing issue? Any insights or troubleshooting steps would be greatly appreciated.
Changing parts solely based on a diagnostic code is not recommended. Please post all relevant error codes and vehicle details so that community members can provide accurate, targeted advice.