P0430
DTC P0420 or P0430
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptors
DTC P0420
-
Catalyst System Low Efficiency Bank 1
DTC P0430
-
Catalyst System Low Efficiency Bank 2
Circuit/System Description
A 3-way catalytic converter controls emissions by converting hydrocarbons and CO into CO2 and NOx into nitrogen. The 3-way catalytic converter also stores oxygen. When the listed idle conditions follow the listed driving conditions the Catalyst System Efficiency test will run. The ECM monitors this oxygen storage capacity by comparing the pre and post-catalyst oxygen sensor signals while adding and subtracting fuel during specific idle conditions. The ECM compares the pre and post-catalyst oxygen sensor signals to determine if the oxygen storage capacity of the catalyst is degraded.
Conditions for Running the DTC
1. Driving Conditions
* DTC P0030, P0031, P0036, P0037, P0038, P042E, P0050, P0053, P0056, P0059, P0060, P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0119, P0120, P0121, P0122, P0123, P0125, P0128, P0130, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P013A, P013B, P013C, P013D, P013E, P013F, P0140, P0141, P014A, P014B, P0151, P0152, P0153, P0154, P0157, P0158, P015A, P015B, P015C, P015D, P0160, P0161, P0171, P0172, P0174, P0175, P0220, P0222, P0223, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0335, P0336, P0340, P0341, P0345, P0346, P0365, P0366, P0390, P0391, P0401, P0403, P0404, P0405, P0443, P0446, P0452, P0502, P0503, P0506, P0507, P0606, P0641, P0651, P0722, P0723, P1133, P1153, P1516, P2A00, P2A03, P2101, P2272, P2273 is not set.
* The engine has been running for greater than 2 minutes.
* The vehicle has been driven at greater than 1,000 RPM with the mass air flow (MAF) greater than 18 g/s for greater than 30 s.
* The engine is operating in closed loop.
* The vehicle has fuel trim learn enabled.
* The engine coolant temperature (ECT) is between 45-128°C (113-262°F).
* The barometric pressure (BARO) is greater than 70 kPa.
* The catalytic converter calculated temperature is at least 420°C (788°F).
* The intake air temperature (IAT) is between -20 and +85°C (-4 and +185°F).
* The battery voltage is greater than 11 V.
2. Idle Conditions
* The vehicle speed is less than 3.2 km/h (2 mph).
* For automatic transmissions, the transmission is in reverse, drive, or low.
* The throttle position is less than 2 %.
* The short term fuel trim is between -10 and +10 %.
* This diagnostic attempts one test during each valid idle period until a pass or fail decision has been reached when the above conditions have been met. This diagnostic attempts up to 8 tests during each drive cycle.
Conditions for Setting the DTC
The ECM has determined the catalyst efficiency has degraded below a calibrated threshold.
Action Taken When the DTC Sets
DTCs P0420 and P0430 are Type A DTCs.
Conditions for Clearing the MIL/DTC
DTCs P0420 and P0430 are Type A DTCs.
Reference Information
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Electrical Information Reference
Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle
Circuit/System Verification
1. Verify that no other DTCs are set.
• If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.
2. Operate the vehicle within the Conditions for Running the DTC while observing the scan tool TWC Mon. OFF Idle Test Conditions Met parameter. The parameter will change to Yes when the OFF Idle Conditions have been met.
• If not the specified value, operate the vehicle within the OFF Idle Conditions.
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 TWC Monitor Test State parameter. When the parameter indicates Active, the TWC Mon Test is running.
6. Continue to monitor the parameter. When the parameter indicates Inactive, the TWC Mon Test has completed.
7. When the test has completed, the TWC Monitor Test Count parameter will increment by one and the TWC Monitor Test Result parameter will indicate Pass, Fail or No Decision.
• If no decision has been made, repeat steps 2-6 until the Test Result parameter indicates a Pass or Fail.
Circuit/System Testing
Caution:
Refer to Three-Way Catalytic Converter Damage Caution Service Precautions.
Caution:
Refer to Heated Oxygen Sensor Resistance Learn Reset Caution Heated Oxygen Sensor Resistance Learn Reset Caution.
1. Inspect for the following conditions, which may cause a catalytic converter to degrade:
* An engine misfire
* High engine oil or high coolant consumption
* Retarded spark timing
* A weak or poor spark
* A lean fuel mixture
* A rich fuel mixture
* A damaged oxygen sensor or wiring harness
* The catalyst test may abort if the vehicle falls outside the conditions for running the DTC.
* A catalyst may be temporarily degraded if a fuel with high sulfur content has been used. Drive the vehicle at highway speeds for 10 minutes and retest the converter.
2. Inspect the catalytic converter for the following conditions:
* Dents
* A severe discoloration caused by excessive temperatures
* Road damage
* An internal rattle caused by damaged catalyst substrate
* Restrictions
• If a condition is found, replace the catalytic converter.
3. Verify the following conditions do not exist with the exhaust system:
* Leaks
* Physical damage
* Loose or missing hardware
* Restrictions
• If a condition is found, repair or replace the affected component as necessary.
4. Verify the following conditions do not exist with the post catalyst HO2S:
* A grounded wiring harness
* Incorrectly torqued HO2S
* Damage
• If a condition is found, repair the condition or replace the post catalyst HO2S as necessary.
5. If all physical conditions test normal, test or replace the catalytic converter.
Repair Instructions
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 h may correct the condition.
* Catalytic Converter Replacement (L20,LMF) Service and RepairCatalytic Converter Replacement (V6) Service and RepairCatalytic Converter Replacement (LGH) Service and RepairCatalytic Converter Replacement (LC8,L96) Service and Repair
* Heated Oxygen Sensor Replacement - Bank 1 Sensor 2 Service and Repair
* Heated Oxygen Sensor Replacement - Bank 2 Sensor 2 Service and Repair
* Exhaust Leakage Testing and Inspection
* Restricted Exhaust Testing and Inspection
Repair Verification
1. Verify that no other DTCs are set.
• If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.
2. Operate the vehicle within the Conditions for Running the DTC while observing the scan tool TWC Mon. OFF Idle Test Conditions Met parameter. The parameter will change to Yes when the OFF Idle Conditions have been met.
• If not the specified value, operate the vehicle within the OFF Idle Conditions.
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 TWC Monitor Test State parameter. When the parameter indicates Active, the TWC Mon Test is running.
6. Continue to monitor the parameter. When the parameter indicates Inactive, the TWC Mon Test has completed.
7. When the test has completed, the TWC Monitor Test Count parameter will increment by one and the TWC Monitor Test Result parameter will indicate Pass, Fail or No Decision.
• If no decision has been made, repeat steps 2-6 until the Test Result parameter indicates a Pass or Fail.