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

Solution

1. Preparation

• Gather tools and parts for the repair.
• Disconnect the negative battery terminal to ensure safety.
• Allow the engine to cool down before starting work.

2. Inspect and Repair Wiring

• Tools Required: Multimeter, wire strippers, electrical tape
• Inspect the wiring harness for the downstream O2 sensor.
  • Look for frays, breaks, or corrosion.
  • Repair or replace damaged wires as necessary.
  • Ensure proper insulation of repaired wires with electrical tape.

3. Replace the Downstream O2 Sensor

• Tools Required: O2 sensor socket, ratchet, torque wrench
• Locate the downstream O2 sensor, usually found in the exhaust pipe after the catalytic converter.
• Using the O2 sensor socket, unscrew the old sensor from the exhaust pipe.
• Apply anti-seize compound to the threads of the new oxygen sensor.
• Install the new sensor into the exhaust pipe and tighten it to the manufacturer's specified torque (usually around 30 ft-lbs).
• Reconnect the electrical connector to the new O2 sensor.

4. Clear the Codes and Test

• Tools Required: OBD-II scanner
• Reconnect the negative battery terminal.
• Use an OBD-II scanner to clear the P0138 code from the ECM.
• Start the engine and let it run for a few minutes to ensure everything is functioning properly.