Circuit/System Testing

NOTE: Notice: In order to avoid damaging the replacement three-way catalytic converter, correct the engine misfire or mechanical fault before replacing the three-way catalytic converter..

NOTE: Refer to Heated Oxygen Sensor (HO2S) Resistance Learn Reset Notice .

IMPORTANT: A new converter with less than 100 miles on it may set P0420 due to out-gassing of the internal matting. Operating the vehicle at highway speeds for approximately 1 hour may correct the condition.

With the engine in closed loop and at operating temperature, increase the engine speed to 1,500 RPM for 1 minute and then return to stabilized idle. Observe that the HO2S 2 voltage parameter is not as active as the HO2S 1 voltage parameter.
- If it is as active then proceed with Circuit/System Verification.
Inspect the catalytic converter for the following conditions:
- Dents
- A severe discoloration caused by excessive temperatures
- Road damage
- An internal rattle caused by damaged catalyst substrate
- Restrictions
  - If a condition is found, replace the catalytic converter.
Inspect the exhaust system for the following conditions:
- Leaks
- Physical damage
- Loose or missing hardware
- Properly torqued HO2S
- If a condition is found, repair the exhaust system.
Inspect the HO2S 2 for the following conditions:
- A grounded wiring harness
- Damage
- If a condition is found, replace the HO2S 2.
- If no physical condition is detected and the HO2S 2 is as active as the HO2S 1 after operating the engine at 1,500 RPM for 1 minute and then returning to a stabilized idle, then replace the catalytic converter.