how to fix the P0135 code in my Volkswagen Golf MK7 (2015-2019)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to ensure safety while working on electrical systems.

2. Inspect and Replace O2 Sensor

• Tools Required: O2 sensor socket, ratchet, torque wrench, multimeter, wire brush.
• Sub-steps:
  1. Locate the upstream O2 sensor (typically situated before the catalytic converter).
  2. Disconnect the electrical connector from the O2 sensor.
  3. Use the O2 sensor socket to unscrew the sensor from the exhaust manifold.
  4. Inspect the threads of the O2 sensor and the mounting hole for carbon buildup. Clean if necessary using a wire brush.
  5. Install the new O2 sensor by screwing it into the mounting hole, ensuring it is snug but do not over-tighten (typically around 30 Nm).
  6. Reconnect the electrical connector securely to the new O2 sensor.

3. Testing

• After replacing the O2 sensor, reconnect the negative battery terminal.
• Start the engine and allow it to reach operating temperature.
• Use the OBD-II scanner to check for any new codes or to verify that the P0135 code has cleared.