my Ram 1500 DT (2019-Present) has a check engine light with code P0420

Solution

1. Preparation

• Gather necessary tools and parts before beginning the repair.
• Disconnect the vehicle battery to prevent electrical shorts.
• Raise the vehicle using a jack and secure it with jack stands.

2. Inspect and Replace Oxygen Sensors (if necessary)

• Tools Required: O2 sensor socket, wrench set, multimeter.
• Sub-steps:
  1. Remove the upstream oxygen sensor by using the O2 sensor socket and wrench.
  2. Install the new oxygen sensor and tighten it to manufacturer's specifications (generally around 30 Nm or 22 lb-ft).
  3. Repeat for the downstream oxygen sensor if it is also faulty.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, exhaust pipe cutter, torque wrench, gaskets.
• Sub-steps:
  1. Disconnect the exhaust pipes from the catalytic converter using the socket set.
  2. Cut and remove the old catalytic converter, if necessary, using an exhaust pipe cutter.
  3. Install the new catalytic converter, ensuring to use new gaskets.
  4. Reconnect the exhaust pipes and torque to the manufacturer’s specifications.

4. Clear Codes and Reconnect Battery

• Sub-steps:
  1. Reconnect the vehicle battery.
  2. Use the OBD-II scanner to clear any stored trouble codes from the vehicle’s computer.