how to fix P0420 code on my Toyota Corolla E140 (2006-2013)

Solution

1. Preparation

• Tools Required: OBD-II scanner, multimeter, socket set, torque wrench, and safety glasses.
• Disconnect the battery to prevent electrical shorts.
• Ensure the vehicle is on a stable surface and raise it if necessary using a jack and jack stands.

2. Inspect and Replace Oxygen Sensors

1. Locate the oxygen sensors: Identify the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
2. Remove the oxygen sensors:
   • Use a socket wrench to unscrew the sensors from their respective locations.
   • Handle sensors carefully to avoid damaging the threads.
3. Test the sensors:
   • Use a multimeter to check the voltage output of the upstream sensor while the engine is running. It should fluctuate between 0.1 to 0.9 volts.
   • Replace any sensor that does not meet this specification.
4. Install new sensors:
   • Apply anti-seize compound on the threads of new sensors.
   • Install the sensors hand-tight, then torque to manufacturer specifications (usually around 30 ft-lbs).

3. Inspect and Replace Catalytic Converter (if necessary)

1. Inspect the catalytic converter:
   • Look for physical damage, such as dents or holes.
   • Check for excessive backpressure by removing the upstream O2 sensor and using a pressure gauge (should be below 1.5 psi at idle).
2. Remove the catalytic converter:
   • Unbolt the converter from the exhaust manifold and mid-pipe using a socket set.
   • If necessary, use penetrating oil to loosen corroded bolts.
3. Install the new catalytic converter:
   • Position the new converter and secure it using new gaskets and bolts.
   • Torque the bolts according to manufacturer specifications (typically around 30-40 ft-lbs).

4. Clear the Codes

• Reconnect the battery and use the OBD-II scanner to clear the P0420 code from the vehicle's computer.