P0420
DTC P0420
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 provide an overview of each diagnostic category.
DTC Descriptor
DTC P0420
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Catalyst System Low Efficiency
Circuit/System Description
The diesel oxidation catalyst, main function is to control emissions of non methane hydrocarbons and soluble organic fraction. Its secondary function is to assist with the diesel particulate filter (DPF) regeneration, by obtaining and sustaining the temperature necessary for regeneration. In order to generate the high exhaust temperatures needed for regeneration, the aftertreatment system increases exhaust temperatures by injecting diesel fuel directly into the exhaust gases entering the DOC. This is accomplished by means of an ECM-controlled fuel injector called the hydrocarbon injector (HCI), also referred to as the indirect fuel injector or exhaust aftertreatment fuel injector. The fuel injector is located in the exhaust pipe upstream of the DOC. The injected fuel is converted into heat by the DOC to incinerate soot accumulated in the DPF. The engine control module (ECM) monitors the exhaust gas temperature sensor 1 and 2 to determine if the operating temperature of the catalyst is achieved during a regeneration event.
The hydrocarbon conversion to oxygen is calculated from the heat flow in the oxidation catalyst, based on measured and modeled temperatures, to determine the efficiency of the oxidation catalyst. The modeled temperatures are calculated using the injection quantity and air mass flow. When the ECM detects that the diesel oxidation catalyst hydrocarbon conversion rate is below a calibrated threshold during an active regeneration event this DTC sets.
Conditions for Running the DTC
* The hydrocarbon converted in the diesel oxidation catalyst is greater than 115 g and the hydrocarbon mass flow is greater than 0.0009 g/s.
* The ECM is commanding a regeneration.
* The exhaust gas temperature sensor 1 is greater than 250°C (482°F).
* The engine speed is between 700-3,400 RPM.
* The barometric pressure (BARO) is greater than 74.8 kPa (10.8 psi).
* The ambient air temperature is greater than -7°C (19.4°F).
* DTC P0420 runs once per driving cycle when the above conditions are met.
Conditions for Setting the DTC
The ECM determines that the efficiency of the diesel oxidation catalyst has degraded below a calibrated threshold.
Action Taken When the DTC Sets
* DTC P0420 is a Type B DTC.
* DPF regeneration is inhibited.
Conditions for Clearing the DTC
DTC P0420 is a Type B DTC.
Diagnostic Aids
* The use of off road red dye fuel or continuing use of non ultra low sulfur fuel may be a contributor to diesel oxidation catalyst failure.
* If exhaust gas temperature sensor 1, 2 or 4 is slow to respond to exhaust gas temperature changes or sticks in range, this DTC may set.
* If exhaust gas temperature sensor 4 is greater than exhaust gas temperature sensor 2 during a DPF regeneration event, the fuel from the indirect fuel injector is being consumed in the DPF. This may indicate that the diesel oxidation catalyst is not functioning properly and should be replaced.
Reference Information
Schematic Reference
Engine Controls Schematics [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views 1-2 Shift Solenoid (SS) Valve (M30)
Description and Operation
Exhaust Aftertreatment System Description Emission Control Systems
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 Control Module References for scan tool information
Circuit/System Verification
1. Ignition ON, observe the DTC information with a scan tool. Verify DTC P003A, P0047, P0048, P0101, P0201-P0208, P02E0, P02E2, P02E3, P02E7-P02E9, P02EB, P0300-P0308, P0402, P0545, P0546, P1048, P1049, P10CC, P10CD, P10CE, P2032, P2033, P2047, P2048, P2049, P20CB, P20CC, P20CD, or P20CE is not set.
• If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.
2. Engine running, observe the DTC information with a scan tool. DTC P0420 should not be set.
3. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing
1. Verify the following conditions do not exist with the exhaust system:
* Exhaust leaks before or after the diesel oxidation catalyst. Refer to Exhaust Leakage Exhaust Leakage for further diagnosis.
* Physical damage
* Loose or missing hardware
• If a condition is found, repair or replace the affected exhaust system components as necessary.
2. Verify the following conditions do not exist with the diesel oxidation catalyst:
* Physical damage or alterations
* Internal rattles caused by a damaged catalyst substrate
* Restrictions
• If a condition is found, replace the diesel oxidation catalyst.
3. Ignition OFF, disconnect the harness connector at the B131 exhaust gas temperature sensor 1, 2 and 4.
4. Measure and record the resistance of the B131 exhaust gas temperature sensor 1, 2 and 4. Compare the measurements to the Temperature Versus Resistance (Fuel Temperature Sensor) Temperature Versus Resistance (Fuel Temperature Sensor)Temperature Versus Resistance (IAT Sensor 1) Temperature Versus Resistance (IAT Sensor 1)Temperature Versus Resistance (EGT Sensors) Temperature Versus Resistance (EGT Sensors)Temperature Versus Resistance (IAT Sensor 2) Temperature Versus Resistance (IAT Sensor 2)Temperature Versus Resistance (ECT Sensors) Temperature Versus Resistance (ECT Sensors)Temperature Versus Resistance (EGR Temperature Sensors) Temperature Versus Resistance (EGR Temperature Sensors) table. The resistance values should be within the specified range indicated in the table.
• If not within the specified range, replace the affected B131 exhaust gas temperature sensor.
5. Observe the scan tool Freeze Frame/Failure Records data for DTC P0420. Determine the temperature difference between EGT Sensor 1 and 2 and between EGT Sensor 2 and 4.
• If EGT Sensor 4 is greater than EGT Sensor 2 by at least 100°C (180° F) and EGT Sensor 2 is within 100°C (180° F) of EGT Sensor 1, replace the diesel oxidation catalyst.
6. Test the Q57 Indirect fuel injector flow. Refer to Indirect Fuel Injector Diagnosis Component Tests and General Diagnostics. Verify the flow amount is at least 17 ml.
• If not within the specified range, replace the Q57 Indirect fuel injector.
7. Verify the following conditions do not exist:
* Off road fuel or red dye fuel
* Low quality B-20 fuel
* Fuel containing high sulfur content
* Engine oil or coolant consumption
* Leaking Q17 fuel injectors-Refer to Fuel Injector Diagnosis Fuel Injector Diagnosis
• If a condition is found, repair as necessary.
Note:
In cold climates diesel fuel may gel in the indirect fuel injector system. This may prevent the injector from operating normally and may cause the DTC to set.
8. If all components test normal and no conditions are found, operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
• If the DTC sets, refer to Circuit/System Testing - step 1
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* Catalytic Converter Replacement (V8) Catalytic Converter ReplacementCatalytic Converter Replacement (V6) Catalytic Converter ReplacementCatalytic Converter Replacement (LGH) Catalytic Converter Replacement
* Exhaust Temperature Sensor Replacement - Position 1 Exhaust Temperature Sensor Replacement - Position 1
* Exhaust Temperature Sensor Replacement - Position 2 Exhaust Temperature Sensor Replacement - Position 2
* Exhaust Temperature Sensor Replacement - Position 4 Exhaust Temperature Sensor Replacement - Position 4
* Perform the scan tool Diesel Particulate Filter (DPF) Regeneration Enable Diesel Particulate Filter (DPF) Regeneration Enable procedure if the scan tool DPF Soot Mass is less than 30 g. If the scan tool DPF Soot Mass is 30 g or greater, perform the Diesel Particulate Filter (DPF) Service Regeneration Diesel Particulate Filter (DPF) Service Regeneration procedure.