what does the code P0138 mean in my Toyota RAV4 XA40 (2013-2018)?

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative terminal of the battery.
• Allow the engine to cool before starting work on the exhaust system.

2. Inspect and Repair Wiring

• Remove any protective covers to access the O2 sensor wiring.
• Inspect the wiring and connectors for damage.
  • If damage is found, repair or replace the affected wires and connectors.
• Ensure all connections are tight and free of corrosion.

3. Replace the Oxygen Sensor

• Locate the upstream O2 sensor (typically near the engine).
• Use an O2 sensor socket to carefully unscrew the old sensor from its mount.
• Apply anti-seize compound to the threads of the new oxygen sensor to facilitate future removal.
• Install the new O2 sensor and tighten it to the manufacturer’s specified torque (usually around 30-35 ft-lbs).
• Reconnect the electrical connector securely.

4. Clear Codes and Test

• Reconnect the negative battery terminal.
• Use an OBD-II scanner to clear the stored trouble codes.
• Start the engine and allow it to reach operating temperature.
• Perform a test drive to ensure the check engine light does not reappear.