Diagnostic Tips For DTC P0420: Catalyst System Low Efficiency (PI1505)

DIAGNOSTIC TIPS FOR DTC P0420: CATALYST SYSTEM LOW EFFICIENCY

TECHNICAL SERVICE BULLETIN

CONDITION/CONCERN

Some customers may comment that the Malfunction Indicator Lamp (MIL) is illuminated.

During diagnosis, a technician may find that DTC P0420 is set or in history.

RECOMMENDATION/INSTRUCTIONS

If DTC P0420 is set, verify that the latest version of Product Emission - Reprogram Engine Control Module campaign (#14801) has been performed.

If campaign #14801A or greater has been performed, continue normal diagnosis referring to SI.

If campaign #14801A or greater has not been completed, perform the latest version of campaign #14801 and in addition complete the following:

1. Install any components that have been removed or replaced during diagnosis.
2. Perform any adjustments, programming or setup procedures that are required when a component is removed or replaced.
3. Clear the DTCs with a scan tool.
4. Turn OFF the ignition for 60 seconds.
5. Operate the vehicle within the Conditions for Running the DTC.
6. Verify the scan tool Catalyst Monitor Not At Idle Test Conditions Met parameter changes to Yes.
   NOTE:

   If YES is not displayed. Refer to Step 5.

7. When the conditions are safe, stop and idle the vehicle in gear (If equipped with automatic transmission) or neutral (If equipped with manual transmission).
8. Verify the Catalyst Monitor Test Result parameter displays Pass when performing the steps listed below:
   1. Apply the service brake.
   2. Monitor the scan tool Catalyst Monitor Test State parameter. When the parameter indicates Active, the Catalyst Monitor Test is running.
      NOTE:

      When the test has completed, the Catalyst Monitor Test Counter parameter will increment by one and the Catalyst Monitor Test Result parameter will indicate Passed, Failed or No Result.

   3. Continue to monitor the parameter. When the parameter indicates Inactive, the Catalyst Monitor Test has completed.
      NOTE:

      If the Catalyst Monitor Test Result parameter indicates No Result, repeat steps 5-8 until the Test Result parameter indicates Passed or Failed.

      NOTE:

      If the Catalyst Monitor Test Result parameter indicates Failed, refer to Circuit/System Testing in SI.

9. If the Catalyst Monitor Test Result parameter indicates Pass, system is all ok.