VIN L

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
- Catalyst System Low Efficiency

Circuit/System Description

The diesel oxidation catalyst, main function is to control emissions of non methane hydro carbons 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. 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.

When the ECM detects that the diesel oxidation catalyst is not reaching a pre-determined temperature 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 during a regeneration event.

Action Taken When the DTC Sets

DTC P0420 is a Type B DTC.

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 or 2 is slow to respond to exhaust gas temperature changes or sticks in range, this DTC may set.

Reference Information
Schematic Reference

Engine Controls Schematics ([1][2]Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector End Views By Name)
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 (Programming and Relearning) 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-P10CE, P2032, P2033, P2047, P2048, P2049 or P20CB-P20CE are 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. Measure and record the resistance of the B131 exhaust gas temperature sensor 1 and 2. Compare the measurements to the Temperature Versus Resistance (IAT Sensor 2) (Temperature Versus Resistance (IAT Sensor 2)) Temperature Versus Resistance (EGT Sensors) (Temperature Versus Resistance (EGT Sensors)) Temperature Versus Resistance (ECT Sensors) (Temperature Versus Resistance (ECT Sensors)) Temperature Versus Resistance (EGR Temperature Sensors) (Temperature Versus Resistance (EGR Temperature Sensors)) Temperature Versus Resistance (EGT Sensors 3 and 4) (Temperature Versus Resistance (EGT Sensors 3 and 4)) Temperature Versus Resistance (Fuel Temperature Sensor) (Temperature Versus Resistance (Fuel Temperature Sensor)) table. The resistance values should be within the specified range indicated in the table.

• If not within the specified range, replace the appropriate exhaust gas temperature sensor.

3. Verify the following conditions, which may cause the diesel oxidation catalyst to degrade, 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
* Q57 Indirect fuel injector leaking or restricted-Refer to Indirect Fuel Injector Diagnosis (Indirect Fuel Injector Diagnosis)
* Leaking Q17 fuel injectors-Refer to Fuel Injector Diagnosis (Fuel Injector Diagnosis)

• If a condition is found, repair as necessary.

4. Verify the following conditions do not exist with the Diesel Oxidation Catalyst:

* Physical damage or alterations
* Internal rattles caused by a damaged catalyst substrate
* Exhaust leaks before or after the diesel oxidation catalyst. Refer to Exhaust Leakage (Exhaust Leakage) for further diagnosis.

• If a condition is found, replace the diesel oxidation catalyst.

5. If all components test normal, replace the diesel oxidation catalyst.

Repair Instructions

* Catalytic Converter Replacement (V6) (Catalytic Converter Replacement) Catalytic Converter Replacement (V8) (Catalytic Converter Replacement) Catalytic Converter Replacement (LMM) (Catalytic Converter Replacement) Catalytic 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)
* 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.