how to fix P0138 code in my Honda Civic 10th Generation (2016-2021)?

Solution

1. Preparation

• Tools Required: OBD-II scanner, multimeter, socket set, torque wrench, oxygen sensor socket, safety goggles, gloves.
• Ensure the vehicle is parked on a flat surface and the engine is cool. Disconnect the negative battery terminal to prevent electrical shock.

2. Inspect Wiring and Connectors

• Sub-steps:
  1. Locate the downstream O2 sensor on the exhaust system.
  2. Visually inspect the wiring harness and connectors for frays, breaks, or corrosion.
  3. Clean any corroded connectors with electrical contact cleaner and ensure a secure connection.

3. Test Oxygen Sensor

• Sub-steps:
  1. Reconnect the battery terminal.
  2. Start the engine and let it reach normal operating temperature.
  3. Use a multimeter to measure the voltage output of the downstream O2 sensor. It should fluctuate between 0.1V and 0.9V.
  4. If the voltage is consistently above 0.8V, the sensor may be faulty.

4. Replace Downstream O2 Sensor (if necessary)

• Sub-steps:
  1. Using an oxygen sensor socket, carefully remove the downstream O2 sensor from the exhaust pipe.
  2. Install the new O2 sensor by hand to avoid cross-threading, then torque it to the manufacturer's specification (usually around 30 ft-lbs).
  3. Reconnect the electrical connector to the new O2 sensor.

5. Clear Codes and Test Drive

• Sub-steps:
  1. Use the OBD-II scanner to clear the P0138 code from the vehicle's computer.
  2. Test drive the vehicle for approximately 20 minutes to ensure the check engine light does not reappear.