P0420
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 oxides of nitrogen NOx into nitrogen. The 3-way catalytic converter also stores oxygen. The ECM monitors this oxygen storage capacity by comparing the pre and post-catalyst oxygen sensor signals while adding and subtracting fuel during specific deceleration fuel cut-off 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
* DTC P0016, P0053, P0054, P0059, P0060, P0068, P0101, P0102, P0103, P0106, P0111, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0128, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P013A, P013B, P013C, P013D, P013E, P013F, P0140, P0141, P014A, P014B, P0151, P0152, P0153, P0154, P0155, P0157, P0158, P0160, P0161, P0171, P0172, P0174, P0175, P0220, P0222, P0223, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0335, P0336, P0340, P0341, P0443, P0606, P0641, P0651, P1133, P1153, P1516, P2101, P2120, P2122, P2123, P2125, P2127, P2128, P2135, P2138, P2176, P2270, P2271, P2272 or P2273 is not set.
* The engine speed is greater than 900 RPM and the vehicle speed is greater than 43 km/h (27 mph) for greater than 20 s.
* The fuel level is greater than 2 % if there is no fuel level DTC set, or greater than 0 % if there is a fuel level DTC set.
* The Engine Coolant Temperature (ECT) is between 73-128°C (164-262°F).
* The Barometric Pressure (BARO) is greater than 70 kPa.
* The catalytic converter calculated temperature is between 525-800°C (977-1,472°F).
* The Intake Air Temperature (IAT) is between -20 and +100°C (-4 and +212°F).
* The battery voltage is more than 11 V.
* Torque request is less than 5 Nm.
* The engine is in a decel fuel cutoff event for greater than 2.35 s.
* The Heated Oxygen Sensor (HO2S) 1 voltage is less than 300 mV prior to decel fuel cutoff exit.
* The HO2S 2 voltage is less than 101 mV for 2.5 s prior to decel fuel cutoff exit.
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.
Diagnostic Aids
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
* High sulfur content fuel
Reference Information
Schematic Reference
Engine Controls Schematics [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views Connector End Views By Name
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Control Module References Programming and Relearningfor scan tool information
Circuit/System Verification
1. Ignition OFF, open the hood to disable the Auto-Stop function. Refer to Hybrid Modes of Operation Description Hybrid Modes of Operation.
2. Ignition ON, verify the scan tool hood position parameter displays Open.
• If the hood position does not display Open, refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle for DTC P254F.
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.
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.
1. Ignition ON, observe the DTC information with a scan tool. Verify that no HO2S or misfire 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. Inspect the catalytic converter for the following conditions:
* Dents
* 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. Inspect the exhaust system for the following conditions:
* Leaks-Refer to Exhaust Leakage Exhaust Leakage.
* Physical damage
* Loose or missing hardware
* Improperly torqued HO2S
* Restrictions-Refer to Restricted Exhaust Restricted Exhaust.
• If a condition is found, repair the exhaust system.
4. Inspect the post catalyst HO2S for the following conditions:
* A grounded or damaged wiring harness
* Damaged sensor
• If a condition is found, replace the post catalyst HO2S.
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 Catalytic Converter Replacement
* Heated Oxygen Sensor Replacement - Bank 1 Sensor 2
* Heated Oxygen Sensor Replacement - Bank 2 Sensor 2