DTC P0420: Catalytic 1/1 Efficiency: Testing
NOTE:
If a O2 sensor or Fuel System Lean DTC(s) is also set, diagnose the other DTC(s) before proceeding. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . Also, check for contaminants that may have damaged O2 sensor and catalytic converter such as contaminated fuel, unapproved silicone, oil and coolant. Repair as necessary
- Ignition on, engine not running. With the DRBIII® scan tool, read DTCs and record the related freeze frame data. Is the Good Trip counter displayed and equal to zero? If yes, go to next step. If no, see INTERMITTENT CONDITION under SELF-DIAGNOSTIC SYSTEM.
- Inspect the Catalytic Converter that is related to the DTC for dents, holes and severe discoloration caused by overheating the Catalytic Converter. Also check if Catalytic Converter is broken internally or leaking. Were any problems found? If yes, replace the Catalytic Converter. Repair the condition that may have caused the failure. If no, go to next step.
- Start the engine. Inspect the exhaust for leak between the engine and the O2 sensor. Inspect the exhaust for leaks between the engine and the appropriate rear O2 sensor. Are there any exhaust leaks? If yes, repair or replace the leaking exhaust parts as necessary. If no, go to next step.
- Check the exhaust for excessive smoke caused by an internal problem in the engine. Is a engine mechanical condition present? If yes, repair the engine mechanical condition as necessary. If no, go to next step.
- A new rear O2 sensor along with an aging front O2 sensor may cause the DTC to set. Review the vehicles repair history. Has the rear O2 sensor been replace without replacing the front O2 sensor? If yes, replace the front O2 sensor as necessary. If no, go to next step.
- There are no other possible causes remaining, replace the Catalytic Converter.