Catalyst Efficiency Fault Codes

Diagnostic Approach — Catalyst Efficiency

1. 1

   Address any misfire codes first — misfires destroy catalytic converters.

2. 2

   Check for oil or coolant consumption — both contaminate the catalyst.

3. 3

   Monitor upstream vs downstream O2 sensor waveforms.

4. 4

   Inspect exhaust for leaks before and after the converter.

5. 5

   If sensors and exhaust are good, replace catalytic converter.