Captiva

DTC P0420 or P0430

A 3-way catalytic converter controls emissions of hydrocarbons, CO and NOx. The catalyst within the converter promotes a chemical reaction, which oxidises the hydrocarbons and the CO that are present in the exhaust gas. This process converts the hydrocarbons and the CO into water vapour and CO2, and reduces the NOx, converting the NOx into nitrogen. The catalytic converter also stores oxygen. The ECM monitors this process by using a heated oxygen sensor (HO2S) that is in the exhaust stream after the 3-way catalytic converter. The HO2S 2 produces an output signal that the ECM uses to calculate the oxygen storage capacity of the catalyst. This indicates the ability of the catalyst to convert the exhaust emissions efficiently. The ECM monitors the efficiency of the catalyst by allowing the catalyst to heat, then wait for a stabilisation period while the engine is idling. The ECM then adds and removes fuel while monitoring the HO2S 2. When the catalyst is functioning properly, the HO2S 2 response to the extra fuel is slow compared to the response of the HO2S 1, which is located before the TWC. When the HO2S 2 response is near that of the HO2S 1, the oxygen storage capability and efficiency of the catalyst may be degraded below an acceptable threshold.

This diagnostic attempts one test during each valid idle period once the above conditions have been met. This diagnostic attempts up to 8 tests during each drive cycle.

The ECM determines that the efficiency of the catalyst has degraded below a calibrated threshold.

DTC P0420 and P0430 are Type A DTCs.

DTC P0420 and P0430 are Type A DTCs.

Inspect for the following conditions, which may cause a catalytic converter to degrade:

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Observe the DTC information with a scan tool. Verify there are no other DTCs set.

⇒	If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle

2. Operate the vehicle within the Conditions for Running the DTC. Observe the scan tool Catalyst Monitor Not At Idle Test Conditions Met parameter. The parameter will change to Yes when the Conditions have been met.

⇒	If not the specified value, operate the vehicle within the Conditions for Running the DTC.

3. When the parameter has changed to Yes and the conditions are safe, stop and idle the vehicle in gear.
4. Apply the service brake.
5. Monitor the scan tool Catalyst Monitor Test State parameter. When the parameter indicates Active, the Catalyst Monitor Test is running.
6. Continue to monitor the parameter. When the parameter indicates Inactive, the Catalyst Monitor Test has completed.
7. When the test has completed, the Catalyst Monitor Test Counter parameters will increment by one and the Catalyst Monitor Test Result parameters will indicate Pass, Fail or No Decision.

⇒	If no decision has been made, repeat steps 2-6 until the Test Result parameters indicate Pass or Fail.

1. Verify the following conditions do not exist with the appropriate catalytic converter:

•

Dents

•	Severe discolouration caused by excessive temperatures

•	Road damage

•	Internal rattles caused by damaged catalyst substrate

•	Restrictions

⇒	If a condition is found, replace the catalytic converter.

2. Verify the following conditions do not exist with the exhaust system:

•

Leaks

•	Physical damage

•	Loose or missing hardware

⇒	If a condition is found, repair the exhaust system.

3. Verify the following conditions do not exist with the appropriate B52B heated oxygen sensor 2:

•	The HO2S is not at the correct torque

•

Damage

⇒	If a condition is found, replace the B52B heated oxygen sensor 2 as necessary.

4. If all physical conditions test normal, test or replace the catalytic converter.

Note: A new converter with less than 100 miles on it may set DTC P0420 or P0430 due to out-gassing of the internal matting. Operating the vehicle at highway speeds for approximately 1 hour may correct the condition.

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 s
5. Operate the vehicle within the Conditions for Running the DTC. Observe the scan tool Catalyst Monitor Not At Idle Test Conditions Met parameter. The parameter will change to Yes when the Conditions have been met.

⇒	If not the specified value, operate the vehicle within the Conditions for Running the DTC.

6. When the parameter has changed to Yes and the conditions are safe, stop and idle the vehicle in gear.
7. Apply the service brake.
8. Monitor the scan tool Catalyst Monitor Test State parameter. When the parameter indicates Active, the Catalyst Monitor Test is running.
9. Continue to monitor the parameter. When the parameter indicates Inactive, the Catalyst Monitor Test has completed
10. When the test has completed, the Catalyst Monitor Test Counter parameters will increment by one and the Catalyst Monitor Test Result parameters will indicate Pass, Fail, or No Decision.

⇒	If no decision has been made, repeat steps 5-9 until the Test Result parameters indicate Pass or Fail.

11. If the repair was related to a DTC, duplicate the Conditions for Running the DTC and use the Freeze Frame/Failure Records, if applicable, in order to verify the DTC does not reset. If the DTC resets or another DTC is present, refer to the Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.