P0420

DTC P0420

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* 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 (DOC), main function is to control emissions of Non Methane Hydro Carbons (NMHC). The secondary function of the DOC 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 (EGT) sensor 1 to determine if the operating temperature of the catalyst is achieved during a regeneration event.

When the ECM detects that the DOC is not reaching a pre-determined temperature during an active regeneration event this DTC runs and fails.

Conditions for Running the DTC

* The engine control module (ECM) must be commanding an active regeneration.
* DTC P0420 runs once during an active regeneration event.

Conditions for Setting the DTC

* The ECM determines that the DOC functionality has degraded below a calibrated threshold, during a regeneration event.
* The condition exists for greater than 4 minutes.

Action Taken When the DTC Sets

* DTC P0420 is a type B DTC.
* DPF regeneration will be inhibited.

Conditions for Clearing the DTC

DTC P0420 is a type B DTC.

Diagnostic Aids

The use of Off Road Red Dye Fuel or non ultra low sulfur fuel the vehicle may be a possible contributor to this DOC failure.

Circuit/System Verification

1. Verify that DTCs P003A, P0047, P0048, P0101, P0201-P0208, P02A1, P02A5, P02A9, P02AD, P02B1, P02B5, P02B9, P02E0, P02E7-P02E9, P029D, P0300-P0308, P0402, P046C, P0545, P0546, P2032, P2033 are not set.

• If any of the DTCs are set, Refer to Diagnostic Trouble Code (DTC) List - Vehicle. Diagnostic Trouble Code Descriptions

2. Verify that exhaust leaks do not exist before the DOC. Refer to Exhaust Leakage.
3. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing

1. Inspect for the following conditions, which may cause a diesel oxidation converter (DOC) to degrade:

* Off Road Fuel or Red Dye Fuel
* Low quality B-20 fuel
* Fuel Containing high sulfur content
* Engine oil or coolant consumption

2. Inspect the DOC for the following conditions:

* Physical damage or alterations
* Internal rattles caused by a damaged catalyst substrate

• If a condition is found, replace the DOC.

3. If all engine and exhaust system test are normal, replace the DOC.

Repair Instructions

Notice: After performing the system repair, perform the following:

* A code clear with a scan tool, regardless of whether or not a DTC is set

* A Diesel Particulate Filter (DPF) Service Regeneration with a scan tool

Perform the above in order to remove soot from the DPF and avoid possible DPF failure.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

* Exhaust Particulate Filter Cleaning (DPF Service Regeneration) Exhaust Particulate Filter Cleaning (DPF Regeneration Enable)
* Catalytic Converter Replacement (Dual Exhaust - Left) Catalytic Converter Replacement (Dual Exhaust - Right) Catalytic Converter Replacement (Single Exhaust - 4.3L, 4.8L and 5.3L) Catalytic Converter Replacement (6.6L (LBZ/LLY)) Catalytic Converter Replacement (6.6L (LMM))
* Exhaust Particulate Filter Cleaning (DPF Service Regeneration) Exhaust Particulate Filter Cleaning (DPF Regeneration Enable) for Service Regeneration Verification Tests