how to fix P0420 code on Toyota Corolla E170 (2013-2019)

Solution

1. Preparation

• Gather tools and parts.
• Disconnect the battery to ensure safety during repair.
• Raise the vehicle using a jack and secure it with jack stands.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• Remove the upstream (pre-catalytic converter) O2 sensor:
  1. Disconnect the electrical connector.
  2. Use the O2 sensor socket to unscrew the sensor from the exhaust manifold.
• Install the new O2 sensor:
  1. Apply anti-seize compound to the threads of the new sensor.
  2. Thread the sensor into the exhaust manifold and tighten to the manufacturer’s torque specification (usually around 30 lb-ft).
  3. Reconnect the electrical connector.
• Repeat for the downstream (post-catalytic converter) O2 sensor if it is also suspected to be faulty.

3. Inspect and Replace the Catalytic Converter

• Tools Required: Socket set, exhaust pipe cutter or saw, gasket scraper.
• Inspect the catalytic converter:
  1. Look for physical damage or severe discoloration.
  2. Tap lightly on the converter; rattling sounds may indicate internal failure.
• If replacement is necessary:
  1. Disconnect the exhaust pipes at both ends of the catalytic converter.
  2. Remove any mounting bolts or brackets securing the converter.
  3. Clean the exhaust pipe flanges.
  4. Install the new catalytic converter, ensuring proper alignment and sealing.
  5. Reconnect and tighten all exhaust connections.

4. Reset the Engine Control Module (ECM)

• Use the OBD-II scanner to clear the P0420 code from the ECM.
• Reconnect the battery.