P0420
DTC P0420 (LUW)
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 Instructionsprovides an overview of each diagnostic category.
DTC Descriptor
DTC P0420
- Catalyst System Low Efficiency
Circuit/System Description
Note: A new converter with less than 160 km (100 mi) on it may set DTC P0420 due to outgassing of the internal matting. Operating the vehicle at highway speeds for approximately 1 h may correct the condition.
A 3-way catalyst controls emissions by converting hydrocarbons and carbon monoxide (CO) into carbon dioxide (CO2), and oxides of nitrogen (NOX) into nitrogen. The 3-way catalyst also stores oxygen. When the listed driving conditions are met, the Catalyst System Efficiency test will run. The engine control module (ECM) monitors this oxygen storage capacity by comparing the pre-catalyst with the post-catalyst oxygen sensor signals while adding and subtracting fuel during specific driving conditions. The ECM compares the pre-catalyst with the post-catalyst oxygen sensor signals to determine if the oxygen storage capacity of the catalyst is degraded.
Conditions for Running the DTC
* DTCs P000A, P000B, P0010, P0013, P0016, P0017, P0030, P0031, P0032, P0036, P0038, P0117, P0118, P0119, P0121, P0122, P0123, P0131, P0132, P0133, P0134, P0135, P0136, P0137, P0138, P0139, P0140, P0141, P0171, P0201, P0202, P0203, P0204, P0221, P0222, P0223, P0261, P0262, P0264, P0265, P0267, P0268, P0270, P0271, P0301, P0302, P0303, P0304, P0335, P0336, P0340, P0365, P0366, P0443, P0446, P0458, P0459, P0496, P0562, P0563, P0642, P0643, P0652, P0653, P0661, P0662, P2088, P2089, P2090, P2091, P2096, P2097, P2100, P2101, P2122, P2123, P2127, P2128, P2176, P2297, P2301, P2303, P2304, P2306, P2307, P2309, P2310, P2A00, P2A0 are not set.
* The engine speed is greater than 1 200 RPM for a minimum of 2 s.
* The vehicle speed is less than 1.24 MPH.
* The intake mass air flow (MAF) is between 2.00-7.00 g/s.
* The vehicle is in closed loop.
* The calculated exhaust mass gas flow is between 5-55.56 g/s, and stable.
* The calculated catalyst temperature is between 480-800°C (896-1 472°F).
* The rear heated oxygen sensor (HO2S) has exceeded the dew point for more than 60 s.
* This diagnostic attempts one test during each period when the above conditions have been met. This diagnostic attempts up to 4 tests during each drive cycle.
Conditions for Setting the DTC
* The ECM has determined the catalyst efficiency has degraded below a calibrated threshold.
* This diagnostic may conclude in 6 test attempts which will require at least 2 drive cycles. However, this diagnostic may require as many as 8 test attempts. Depending on driving conditions, more than 2 drive cycles may be required. Each test attempt may conclude within approximately 1 min
Action Taken When the DTC Sets
DTC P0420 is a Type A DTC.
Conditions for Clearing the DTC
DTC P0420 is a Type A DTC.
Reference Information
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
* Heated Oxygen Sensor Wiring Repairs Heated Oxygen Sensor Wiring Repairs
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References Control Module Referencesfor scan tool information
Circuit/System Verification
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 160 km (100 mi) on it may set DTC P0420 due to outgassing of the internal matting. Operating the vehicle at highway speeds for approximately 1 h may correct the condition.
1. If any other DTCs are set perform those diagnostics first.
2. Inspect for the following conditions which may cause a catalyst 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 min and retest the converter.
3. Operate the vehicle within the conditions for running the DTC.
• If the DTC fails this key cycle, continue with this procedure.
4. Inspect the catalyst for the following conditions:
* Dents
* A discoloration of the catalyst caused by higher temperatures as the customer may desire
* Road damage
* An internal rattle caused by damaged catalyst substrate
* Restrictions
• If a condition is found, replace the catalyst.
5. Inspect the exhaust system for the following conditions:
* Leaks
* Physical damage
* Loose or missing hardware
* Properly torqued B52A Heated Oxygen Sensor 1
* Restrictions
• If a condition is found, repair the exhaust system.
6. Inspect the B52B Heated Oxygen Sensor 2 for the following conditions:
* A grounded wiring harness
* Damage
• If a condition is found, replace the B52B Heated Oxygen Sensor 2.
• If no physical condition is detected, replace the catalyst.
Repair Instructions
Note: A new converter with less than 160 km (100 mi) on it may set DTC P0420 due to outgassing of the internal matting. Operating the vehicle at highway speeds for approximately 1 h may correct the condition.
* Catalytic Converter Replacement (LDE, LXV, 2H0, LUW and LFH) Service and RepairCatalytic Converter Replacement (1.4L LUH and LUJ) Service and Repair
* Heated Oxygen Sensor Replacement - Sensor 2 Heated Oxygen Sensor Replacement - Sensor 2
Repair Verification
1. Clear the DTCs.
2. Operate the vehicle within the Conditions for Running and Setting for at least 10 min.
3. Stop the vehicle.
4. Engine OFF, allow the ECM to power down.
5. Operate the vehicle within the Conditions for Running and Setting for at least 10 min. DTC P0420 should run and pass.