Test Description

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1  - The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store freeze frame data, if applicable. This creates an electronic copy of data taken when fault occurred. The information is then stored in the scan tool for later reference.
2. 3  - This step verifies whether malfunction is presently occurring.
3. 4  - This step checks whether malfunction that caused DTC P0420 is still present. The catalytic converter diagnostic can be monitored on scan tool under I/M SYSTEM INFORMATION. When Catalyst test displays a YES status, indicating the catalytic converter diagnostic is completed, check for DTC P0420 in LAST TEST FAILED screen of scan tool. If there is no DTC P0420 displayed Catalyst diagnostic has run and passed, indicating that no malfunction was present this time. DTCs MUST be cleared to view CURRENT STATUS of system diagnostics being performed. Do not forget the I/M System Information tests only indicate that test has run, not if test passed or failed. LAST TEST FAILED screen must be checked for related DTCs to determine the outcome of the diagnostic test involved.