02 Suburban PO430 Code: Oxygen Sensor or Catalytic Converter Issue?
I'm experiencing a recurring PO430 diagnostic code on my 2002 Suburban. I replaced the oxygen sensor and cleared the code, but it returned within 45 minutes of driving. The truck has only 40,000 miles and runs smoothly with no performance issues—only the check engine light remains on. Given that the vehicle is not showing any drivability problems, I'm concerned about a failing catalytic converter rather than a sensor issue. Is there a way to confirm whether the code is related to the oxygen sensor or the catalytic converter? Any advice on how to properly diagnose this would be greatly appreciated.
What size engine do you have? Are you using a personal OBD2 scanner? If so, ensure it can monitor both oxygen sensors and catalytic converter (cat) monitors. On your 2002 Suburban, the upstream oxygen sensors are labeled O2S11 and O2S21, while the downstream cat monitors—located after the catalytic converter—are labeled O2S12 and O-2S22 if you have two. If a catalytic converter is failing, the cat monitor reading will match the upstream sensor reading. Remember: oxygen sensors are located before the catalytic converter, while cat monitors are positioned after it.