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 - Right Side
DTC P0430
- Catalyst System Low Efficiency Bank 2 - Left Side
Circuit/System Description
A 3-way catalytic converter controls emissions of hydrocarbons, CO and NOx. The catalyst within the converter promotes a chemical reaction, which oxidizes the hydrocarbons and the CO that are present in the exhaust gas. This process converts the hydrocarbons and the CO into water vapor and CO2, and reduces the NOx, by 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 stabilization 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 3-way catalytic converter. 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.
Conditions for Running the DTC
* Before the ECM can report DTC P0420 or P0430 failed, DTCs P0030, P0031, P0032, P0036, P0037, P0038, P0050, P0051, P0052, P0056, P0057, P0058, P0100, P0101, P0102, P0103, P0121, P0122, P0123, P0131, P0132, P0133, P0135, P0137, P0138, P0140, P0141, P0151, P0152, P0153, P0155, P0157, P0158, P0160, P0161, P0221, P0222, P0223, P0335, P0336, P0338, P2096, P2097, P2098, P2099, P2195, P2196, P2197, P2198, P2232, P2235, P2237, P2240, P2243, P2247, P2251, P2254, P2270, P2271, P2272, P2273, P2297, P2298, P2626, and P2629 must run and pass.
* DTC P0010, P0011, P0013, P0014, P0020, P0021, P0023, P0024, P0030, P0031, P0032, P0050, P0051, P0052, P0100, P0101, P0102, P0103, P0116, P0117, P0118, P0119, P0121, P0122, P0123, P0128, P013A, P013C, P013E, P0130, P0131, P0132, P0133, P0135, P0137, P0138, P014A P0140, P0141, P0150, P0151, P0152, P0153, P0155, P0157, P0158, P0160, P0161, P0221, P0222, P0223, P0300, P0301-P0306, P0443, P0455, P0458, P0459, P0496, P0497, P2088, P2089, P2090, P2091, P2092, P2093, P2094, P2095, P2096, P2097, P2098, P2099, P2100, P2101, P2107, P2119, P2122, P2123, P2127, P2128, P2138, P2176, P2177, P2178, P2179, P2180, P2187, P2188, P2189, P2190, P2232, P2235, P2270, P2271, P2272, or P2273 is not set.
* The engine speed is between 1,040-2,360 RPM.
* The engine load is between 17-60 %.
* The air flow into the engine is between 4-21 g/s and steady.
* The ambient air temperature is warmer than -30°C (-22°F).
* The HO2S 2 is at operating temperature for greater than a range of 140-210 s.
* The engine is operating in Closed Loop.
* The calculated 3-way catalytic converter temperature is between 480-760°C (896-1,400°F) and steady for greater than 5 s.
* The above conditions exist for approximately 17 minutes.
* DTCs P0420 and P0430 run once per drive cycle when the above conditions are met. The ECM will attempt to run this diagnostic up to 3 times per drive cycle.
Conditions for Setting the DTC
The ECM determines the oxygen storage capacity of the catalyst has degraded below a calibrated threshold. The DTC sets when the condition exists during the sample period, then a 5 s delay for the MIL.
Action Taken When the DTC Sets
DTCs P0420 and P0430 are Type A DTCs.
Conditions for Clearing the 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
* A damaged oxygen sensor or wiring harness
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)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Testing
1. Observe the DTC information with a scan tool. Verify there are no HO2S, fuel system, or misfire DTCs set.
• If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle (Diagnostic Trouble Code (DTC) List - Vehicle) to diagnosis the applicable DTC, before proceeding with this diagnostic procedure.
2. Verify the following conditions do not exist with the catalytic converter:
* Dents
* A severe discoloration caused by excessive temperatures
* Road damage
* An internal rattle caused by damaged catalyst substrate
* Restrictions
• If a condition is found, repair as necessary.
3. Verify the following conditions do not exist with the exhaust system:
* Leaks
* Physical damage
* Loose or missing hardware
* Improperly torqued HO2S
• If a condition is found, repair the exhaust system.
4. Verify the following conditions do not exist with the HO2S 2:
* A grounded wiring harness
* Damage
• If a condition is found, replace the HO2S 2.
5. If no physical condition is detected and the HO2S 2 is as active as the HO2S 1 after operating the engine at 1,500 RPM for 1 minute and then returning to a stabilized idle, then replace the appropriate catalytic converter.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Restricted Exhaust (Restricted Exhaust)
* Exhaust Leakage (Exhaust Leakage)
* Heated Oxygen Sensor Replacement - Bank 1 Sensor 2 (Heated Oxygen Sensor Replacement - Bank 1 Sensor 2)
* Heated Oxygen Sensor Replacement - Bank 2 Sensor 2 (Heated Oxygen Sensor Replacement - Bank 2 Sensor 2)
* Catalytic Converter Replacement - Left Side (LLT) (Catalytic Converter Replacement - Left Side)Catalytic Converter Replacement - Left Side (L99/LS3) (Catalytic Converter Replacement - Left Side)
* Catalytic Converter Replacement - Right Side (LLT) (Catalytic Converter Replacement - Right Side)Catalytic Converter Replacement - Right Side (L99/LS3) (Catalytic Converter Replacement - Right Side)