how to fix P0420 in Toyota Corolla E170 (2013-2019) after replacing catalytic converter

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the battery to prevent any electrical shorts.

Tools Required:

• OBD-II scanner
• Multimeter
• Socket set
• Torque wrench
• Exhaust leak detection tool

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.
• Check the downstream sensor; it should remain relatively stable (around 0.5V).
• If the downstream sensor fluctuates like the upstream, it may indicate a problem.

3. Repair or Replace Faulty Components

• If the oxygen sensors are faulty:

  1. Disconnect the electrical connectors from both sensors.
  2. Remove the sensors using a socket wrench.
  3. Install new sensors and torque them to the manufacturer’s specifications (generally around 30 ft-lbs).
  4. Reconnect the electrical connectors ensuring a secure fit.

• If exhaust leaks are detected:

  1. Inspect exhaust manifold, pipes, and connections for any cracks or holes.
  2. Replace damaged components or use exhaust sealant as necessary.

4. Reset the Engine Control Module (ECM)

• Reconnect the battery.
• Use the OBD-II scanner to clear the P0420 code from the ECM.
• Start the vehicle and allow it to reach operating temperature.