my Ram 1500 DT (2019-Present) has a P0420 code after replacing the cat, what now?

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the battery to ensure safety while working on the vehicle.
• Tools Required: OBD-II scanner, socket set, torque wrench, multimeter, exhaust leak detector.

2. Inspect and Replace Oxygen Sensors

• Sub-steps:
  1. Locate the upstream and downstream oxygen sensors. They are usually positioned before and after the catalytic converter.
  2. Disconnect the electrical connectors from both oxygen sensors.
  3. Use a socket or wrench to remove the sensors from the exhaust system.
  4. Install new sensors using the manufacturer's specifications for torque (typically around 30 lb-ft).
  5. Reconnect the electrical connectors ensuring they are secure.

3. Check for Exhaust Leaks

• Sub-steps:
  1. With the engine running, use an exhaust leak detector or soapy water to identify any leaks near the catalytic converter and exhaust joints.
  2. If leaks are detected, repair or replace the affected components (e.g., gaskets, pipes).
  3. Tighten any loose clamps or bolts to manufacturer specifications.

4. Reset the Engine Control Module (ECM)

• Sub-steps:
  1. Reconnect the battery.
  2. Use an OBD-II scanner to clear the P0420 code and reset the ECM.
  3. Drive the vehicle for a short trip to allow the ECM to re-evaluate the system.