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

Solution

1. Preparation

• Gather all necessary tools and replacement parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool down completely.

2. Inspect and Replace Oxygen Sensors

1. Locate the Oxygen Sensors: Identify the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
2. Disconnect the Sensors: Unplug the electrical connectors from both oxygen sensors.
3. Remove the Sensors: Use an O2 sensor socket to carefully unscrew and remove the sensors from the exhaust manifold and catalytic converter.
4. Install New Sensors: Apply anti-seize compound on the threads of the new sensors, then install them securely into their respective positions.
5. Reconnect the Electrical Connectors: Ensure the connectors are firmly connected to the new sensors.

3. Inspect and Replace the Catalytic Converter (if necessary)

1. Inspect the Catalytic Converter: Check for physical damage, rattling sounds, or any signs of clogging.
2. Remove the Old Catalytic Converter:
   • Loosen and remove the bolts securing the catalytic converter to the exhaust system using a socket set.
   • Carefully detach the converter from the exhaust pipes.
3. Install the New Catalytic Converter:
   • Position the new catalytic converter in place.
   • Secure it with the original bolts, tightening them to the manufacturer’s specifications (typically 30-40 lb-ft).
4. Reattach Exhaust Components: If any exhaust hangers were disconnected, reattach them.

4. Reset the Check Engine Light

1. Reconnect the Battery: Connect the negative battery terminal back.
2. Clear the Codes: Use the OBD-II scanner to clear the P0420 code and any other stored codes.
3. Test Drive the Vehicle: Drive the vehicle for a short distance to allow the ECU to re-evaluate the system.