Circuit/System Testing

WARNING: This page is about a different variant/trim than selected.

Verify the following conditions do not exist with the air induction system and exhaust system:
- Induction system leaks - Refer to Induction System Smoke Test in Charge Air Cooler Diagnosis (Induction System Air Leak Test) , Charge Air Cooler Diagnosis (Induction System Smoke Test) and Charge Air Cooler Diagnosis .
- Exhaust leaks before or after the diesel oxidation catalyst. Refer to 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.
- If no condition is found
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.
- If no condition is found
Observe the scan tool Freeze Frame/Failure Records data for DTC P0420. Determine the temperature difference between EGT Sensor 1 and 2 and EGT Sensor 2 and 3.
- If EGT Sensor 3 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.
- If EGT Sensor 3 is not greater than EGT Sensor 2 by at least 100°C (180°F) and EGT Sensor 2 is at least 100°C (180°F) greater than EGT Sensor 1
Verify the following conditions do not exist:
- Off road fuel or red dye fuel.
- Low quality B20 fuel.
- Fuel containing high sulfur content.
- Engine oil or coolant consumption.
- If a condition is found
  Repair as necessary.
- If no condition is found
If all components test normal and no conditions are found, 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.
- If the DTC sets
  Refer to Circuit/System Testing - step 1
- If the DTC does not set
All OK.