how to fix P0420 code on Toyota Corolla E210 (2019-2024)

Solution

1. Preparation

• Gather tools: OBD-II scanner, socket set, torque wrench, multimeter, safety glasses, gloves.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect O2 Sensors

• Upstream O2 Sensor:

  1. Locate the upstream O2 sensor near the exhaust manifold.
  2. Disconnect the electrical connector.
  3. Use a multimeter to check the voltage; it should fluctuate between 0.1V and 0.9V.
  4. If faulty, replace it with a new sensor, torque to manufacturer specifications.

• Downstream O2 Sensor:

  1. Locate the downstream O2 sensor after the catalytic converter.
  2. Disconnect the electrical connector.
  3. Check voltage in the same manner; if it does not fluctuate or is consistently low, replace it.
  4. Torque the new sensor to manufacturer specifications.

3. Inspect and Replace Catalytic Converter

1. If O2 sensors are functional, inspect the catalytic converter:
   • Look for physical damage, such as dents or cracks.
   • If found damaged, proceed to replacement.
2. Remove the exhaust pipes connected to the catalytic converter using a socket set.
3. Unbolt the catalytic converter from its mounting points.
4. Install the new catalytic converter, ensuring the gasket is in place and secure.
5. Torque bolts to the manufacturer’s specifications.

4. Reconnect Battery and Clear Code

1. Reconnect the negative battery terminal.
2. Use the OBD-II scanner to clear the P0420 code.
3. Perform a test drive to confirm the repairs.