P0420

P0420-CATALYST EFFICIENCY BANK 1
For a complete wiring diagram, refer to the Wiring Information Electrical Diagrams.
Theory of Operation

The Aftertreatment Diesel Oxidation Catalyst is designed to react with hydrocarbons in the exhaust stream, this chemical reaction reduces hydrocarbon emission levels and also produces heat. Periodically, the Engine Control Module (ECM) will utilize the heat generated by this reaction in the Aftertreatment Diesel Oxidation Catalyst to actively regenerate and clean the Aftertreatment Diesel Particulate Filter. This diagnostic checks that the Aftertreatment Diesel Oxidation Catalyst is present and functioning correctly. The ECM monitors the efficiency of the Aftertreatment Diesel Oxidation Catalyst for DC and DM models through interpretation of data received from the Aftertreatment Diesel Oxidation Catalyst inlet and Aftertreatment Diesel Particulate Filter inlet temperature sensors for DH and D1 models the DOC inlet temperature is calculated by the ECM, the monitor checks for a temperature rise across the Aftertreatment Diesel Oxidation Catalyst. The ECM will set the fault if it detects that the Aftertreatment Diesel Oxidation Catalyst is not present in the aftertreatment/exhaust system. The ECM will illuminate the MIL lamp immediately when the diagnostic runs and fails. The ECM will turn off the MIL lamp immediately after the diagnostic runs and passes.

- When Monitored:
This diagnostic runs when the engine is running, and performing an active regeneration of the Aftertreatment Diesel Particulate Filter.

- Set Condition:
The Engine Control Module (ECM) will set the fault if it detects that the Aftertreatment Diesel Oxidation Catalyst is not present in the aftertreatment/exhaust system.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

1. OTHER DTCS
1. Ignition on, engine not running.
2. With the scan tool, read DTCs.

Are any other DTCs Active?

Yes

- Repair other DTCs before proceeding.

No

- Go To 2

2. EXHAUST LEAK
1. Perform the no trouble code test CHECKING THE EXHAUST SYSTEM FOR LEAKS. Checking the Exhaust System For Leaks.

Are leaks found?

Yes

- Repair or replace as necessary.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 3

3. EXHAUST GAS TEMPERATURE SENSOR 1 AND 2 ARE FUNCTIONAL
1. For Automatic Transmission Vehicle.
- Run the engine at Idle for at least 10 to12 minutes with the vehicle in PARK.
- Check that Exhaust Temperature Sensor 1 and Exhaust Temperature Sensor 2 are within 150°F - 200°F of each other.

2. For Manual Transmission Vehicle.
- Run the engine at Idle for at least 10 to12 minutes with the PARKING BRAKE ON.
- Check that Exhaust Temperature Sensor 1 and Exhaust Temperature Sensor 2 are within 150°F - 200°F of each other.

Is Exhaust Temperature Sensor 1 and Exhaust Temperature Sensor 2 are within 150°F - 200°F of each other?

Yes

- Go To 4

No

- Replace both Exhaust Temperature Sensors.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

4. AFTERTREATMENT DIESEL OXIDATION CATALYST IS DAMAGED OR NOT FUNCTIONING PROPERLY
1. Remove the exhaust plumbing from the Turbocharger outlet.
2. Inspect for signs of oil, coolant or fuel being introduced into the aftertreatment system from the engine or signs of moisture in the Turbocharger exhaust outlet.

Is contamination found in the turbocharger exhaust outlet?

Yes

- Identify and repair the source of the contamination within the engine and replace the Aftertreatment Diesel Oxidation Catalyst after the engine failure has been repaired.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 5

5. AFTERTREATMENT DIESEL OXIDATION CATALYST INLET AND/OR OUTLET TEMPERATURE SENSORS
1. Remove the Aftertreatment Diesel Oxidation Catalyst and temperature sensors and inspect for damage and presence of face plugging.

Are the components found to be missing, plugged or damaged during the inspection of the Aftertreatment Diesel Oxidation Catalyst and temperature sensors?

Yes

- Replace or repair damaged component(s).
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 6

6. AFTERTREATMENT DIESEL PARTICULATE FILTER MOBILE DESOOT
1. Perform a mobile desoot of the Aftertreatment Diesel Particulate Filter.
2. With the scan tool, read DTCs and one trip failures.

Is P0420 set as a DTC or one trip failure?

Yes

- Replace Aftertreatment Diesel Oxidation Catalyst then clear the DTC.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Test complete.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.