why is my Tesla Model 3 Original (2017-2023) check engine light on with code P0420

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to ensure safety while working on electrical components.

2. Inspect Oxygen Sensors

• Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
• Using a multimeter, check the voltage output of the upstream sensor; it should fluctuate between 0.1V to 0.9V.
• If the voltage is static or outside this range, replace the sensor.
• Repeat the check for the downstream sensor; it should have a steady voltage typically around 0.5V.

3. Examine the Catalytic Converter

• Inspect the catalytic converter for physical damage, such as dents or cracks.
• If found damaged, proceed to replace the catalytic converter:
  • Remove the exhaust pipes connected to the catalytic converter using a socket set.
  • Unbolt the catalytic converter from its mounting points.
  • Install the new catalytic converter and torque the bolts to the manufacturer's specifications (usually around 25-35 lb-ft).

4. Reconnect Components

• Reconnect the upstream and downstream oxygen sensors if they were removed.
• Reconnect the negative battery terminal.

5. Clear Error Codes

• Use the OBD-II scanner to clear the P0420 code from the vehicle’s computer.
• Monitor the system for any reoccurrence of the code.