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Home >> Pontiac >> 2007 >> Vibe Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System & Fuel System - DTC P0134 To DTC P0451 >> DTC P0420 >> Test Description

Test Description

The numbers below refer to the step numbers on the diagnostic table.

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

Step Action Yes No
1  Did you perform the Diagnostic System Check - Vehicle? Go to Step 2  Go to Diagnostic System Check - Vehicle
2 Check any for any HO2S DTCs and diagnose those DTCs first.
Are DTCs P0130, P0133, P0135, P0136, or P0141 set?		 Go to Diagnostic Trouble Code (DTC) List - Vehicle Go to Step 3 
3 
  1. Install a scan tool.
  2. Start the engine.
  3. Run the engine until normal operating temperature is reached.
  4. Check that the engine is operating in Closed Loop.
  5. Run the engine at 2,500-3,000 RPM for 3 minutes.
  6. Monitor the HO2S 1 and the HO2S 2 signals on the scan tool.
Is the HO2S 2 signal as active as the HO2S 1 signal?		 Go to Step 5  Go to Step 4 
4 
  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC or until the Catalyst test is complete. Review the supporting text.
Did a DTC P0420 set?		 Go to Step 5  Go to Diagnostic Aids
5
  1. Visually and physically inspect the 3-way catalytic converter for the following concerns:
    • Any dents
    • A severe discoloration caused by excessive temperatures
    • Any holes
    • An internal rattle caused by a damaged catalyst
  2. Check that the 3-way catalytic converter is a high quality part and meets OEM specifications.
Was a problem found?		 Go to Step 8  Go to Step 6 
6
  1. Visually and physically inspect the exhaust system for any of the following conditions:
    • Any leaks
    • Any damage
    • Any loose or missing hardware
  2. Repair as necessary.
Was a repair necessary?		 Go to Step 9  Go to Step 7 
7
  1. Visually and physically inspect the heated oxygen sensor (HO2S) 2 for the following conditions:
    • The pigtail and the wiring harness making contact with the exhaust pipe
    • A loose HO2S 2
    • Any road damage
  2. Repair as necessary.
Was a repair necessary?		 Go to Step 9  Go to Step 8 
8
IMPORTANT: Locate and repair the cause of the catalytic converter failure before installing the replacement converter.
Replace the 3-way catalytic converter. Refer to Catalytic Converter Replacement (LV6 Engine) .Is the action complete?		 Go to Step 10  -
9
  1. Start the engine.
  2. Run the engine until normal operating temperature is reached.
  3. Check that the engine is operating in Closed Loop.
  4. Run the engine at 2,500-3,000 RPM value for 3 minutes.
  5. Monitor the HO2S 1 and the HO2S 2 signals on the scan tool.
Is the HO2S 2 signal as active as the HO2S 1 signal?		 Go to Diagnostic Aids Go to Step 10 
10
  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC or until the Catalyst test is complete. Review the supporting text.
Does the DTC run and pass?		 Go to Step 11  Go to Step 2 
11 With a scan tool, observe the stored information, Capture Info.
Does the scan tool display any DTCs that you have not diagnosed?		 Go to Diagnostic Trouble Code (DTC) List - Vehicle System OK
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