how to fix the P0138 code on my Toyota RAV4 Fifth Generation (2019-present)

Solution

1. Preparation

• Tools Required: OBD-II scanner, multimeter, socket set, torque wrench, oxygen sensor socket.
• Allow the engine to cool before starting work.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Remove the Faulty Oxygen Sensor

• Locate the upstream oxygen sensor (Bank 1, Sensor 2) in the exhaust system.
• Use an oxygen sensor socket to carefully unscrew and remove the sensor from the exhaust pipe.
• Inspect the sensor and wiring for any signs of damage.

3. Install the New Oxygen Sensor

• Apply anti-seize compound to the threads of the new oxygen sensor (if applicable).
• Screw the new oxygen sensor into the exhaust pipe by hand to avoid cross-threading.
• Use a torque wrench to tighten the sensor to the manufacturer’s specified torque (typically around 30-40 ft-lbs).
• Reconnect the electrical connector securely.

4. Reconnect the Battery and Clear Codes

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0138 code from the ECU.
• Start the engine and allow it to run for a few minutes to check for any new codes.

5. Final Inspection

• Check for any exhaust leaks around the newly installed sensor.
• Verify that the check engine light remains off after several drive cycles.