how to fix P0420 code in Volkswagen Tiguan First Generation (2007-2018)

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the battery to prevent electrical shorts.
• Raise the vehicle using a hydraulic jack and secure it with jack stands.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, wrench set.
• Remove the upstream oxygen sensor:
  1. Locate the upstream O2 sensor (before the catalytic converter).
  2. Use the O2 sensor socket to unscrew and remove it.
  3. Install the new upstream oxygen sensor and torque to manufacturer specifications (typically around 30 Nm).
• Remove the downstream oxygen sensor:
  1. Locate the downstream O2 sensor (after the catalytic converter).
  2. Repeat the removal process as above.
  3. Install the new downstream oxygen sensor and torque as specified.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, exhaust pipe cutter (if needed), gasket scraper.
• Remove the catalytic converter:
  1. Disconnect any oxygen sensors connected to the catalytic converter.
  2. If applicable, cut the exhaust pipe on both sides of the catalytic converter (ensure to leave enough pipe for the new connection).
  3. Unbolt the catalytic converter from the exhaust manifold and exhaust pipe.
• Install the new catalytic converter:
  1. Position the new catalytic converter in place.
  2. Bolt it to the exhaust manifold and the exhaust pipe, ensuring gaskets are correctly placed.
  3. Torque bolts to the manufacturer-specified values (usually around 25-30 Nm).
• Reinstall any oxygen sensors removed earlier.

4. Reconnect Battery and Clear Codes

• Reconnect the battery.
• Use an OBD-II scanner to clear the P0420 code and any other related codes.