Nissan Sentra GXE P0300 and P0430 Codes: Causes, Fixes, and What to Check
I own a 2002 Nissan Sentra GXE and have been experiencing persistent Check Engine Light issues. The light has remained on for an extended period due to financial constraints, but the vehicle has otherwise started reliably with no noticeable power loss. Recently, however, I've noticed starting difficulties—though it often starts on the first attempt, it struggles to maintain idle, smoothing out after about one minute. Most recently, the engine turned over but failed to start at all. I used an OBDII scanner and retrieved two diagnostic codes: P0300 (Cylinder Misfire Detected) and P0430 (Catalyst System Efficiency Below Threshold - Bank 2). I'm looking for guidance on what components to inspect or replace, and which troubleshooting steps are most effective. Any insights into the root cause of these issues would be greatly appreciated. Thanks in advance!
It's important to check when the last tune-up was performed. Ensure you're using high-quality spark plugs and other OEM-recommended parts, as substandard components can cause misfires. Given that the Check Engine Light has been on for a long time, it's likely that the catalytic converter on Bank 2 has been damaged by repeated misfires and may need replacement. Also, verify if your OBDII scanner can monitor engine temperature, open-loop vs. closed-loop operation, and oxygen sensor activity—this data helps diagnose whether the issue is related to fuel mixture or sensor performance. Best of luck, and feel free to update us on any progress you make.