why is my Honda CR-V check engine light on with code P0420

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the battery to prevent any electrical shorts.
• Allow the exhaust system to cool before working on it.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• Remove the upstream oxygen sensor:
  1. Locate the upstream oxygen sensor (usually before the catalytic converter).
  2. Use the O2 sensor socket to unscrew and remove it.
• Install the new upstream oxygen sensor:
  1. Apply anti-seize compound to the threads of the new sensor.
  2. Hand-tighten it into the exhaust manifold, then torque it to the manufacturer's specification (typically around 30 lb-ft).
• Repeat the process for the downstream oxygen sensor if necessary.

3. Inspect and Replace Catalytic Converter

• Tools Required: Socket set, jack and jack stands, exhaust pipe cutter (if needed).
• Inspect the catalytic converter for physical damage or blockage:
  1. Check for rattling sounds while shaking the converter.
  2. Measure exhaust back pressure to check for clogs (should be below 2.5 psi at idle).
• If replacement is needed:
  1. Cut the exhaust pipes before and after the catalytic converter.
  2. Remove the old catalytic converter.
  3. Install the new catalytic converter, ensuring proper alignment.
  4. Reconnect the exhaust pipes and torque to specification.

4. Clear Codes

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