how to fix P0420 code on my Ram 1500 DT (2019-Present)

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the battery to ensure safety while working on electrical components.
• Ensure the vehicle is parked on a flat surface and secure it with wheel chocks.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, socket set, torque wrench
• Remove the upstream (pre-catalytic) oxygen sensor:
  1. Use the O2 sensor socket to unscrew the sensor from the exhaust manifold.
  2. Inspect the sensor for damage or carbon buildup.
  3. If faulty, replace it with a new sensor.
  4. Torque the new sensor to the manufacturer’s specification (usually around 30-40 lb-ft).
• Repeat the process for the downstream (post-catalytic) oxygen sensor.

3. Inspect and Replace Catalytic Converter

• Tools Required: Wrench set, exhaust pipe cutter, exhaust gasket set
• Remove the catalytic converter:
  1. Use an exhaust pipe cutter to cut the exhaust pipes leading to and from the catalytic converter.
  2. Unbolt the converter from its mounting points using a wrench.
  3. Inspect for clogs or damage; if found, replace with a new unit.
  4. Install the new catalytic converter, ensuring it is properly aligned and secured.
  5. Use new gaskets to prevent leaks at both ends and torque bolts to specified values.

4. Reconnect Battery and Clear Codes

• Reconnect the vehicle's battery.
• Use the OBD-II scanner to clear any existing trouble codes.
• Start the engine and let it idle for a few minutes to ensure everything operates correctly.