how to fix P0138 code in Honda Civic 9th Generation (2012-2015)

Honda Civic 10th Generation (2016-2021)

Error Codes

1-2 hours

Time

medium

Difficulty

medium

Severity

Error Code: P0138

3 min read

571 words

Problem Statement

Learn how to diagnose and fix P0138 oxygen sensor issues in Honda Civic 2012-2015. Step-by-step guide with diagnostic procedures and repair instructions.

Error Code

P0138

Affected Component

Exhaust System

Estimated Time

1-2 hours

⚠️ Safety Warnings

Important safety information - read before proceeding

•Disconnect the battery before working on electrical systems.
•Allow the engine to cool before opening the exhaust system to prevent burns.

Symptoms

•Check engine light illuminated
•Poor fuel economy
•Engine hesitation during acceleration
•Failed emissions test
•Rich fuel mixture indicated by odor of fuel

Diagnostic Steps

1
Scan for error codes using an OBD-II scanner to confirm P0138 and check for other related codes.
2
Inspect the wiring and connectors of the downstream oxygen sensor for any signs of damage, corrosion, or loose connections.
3
Measure the voltage output of the downstream O2 sensor using a multimeter to verify if it is consistently high (above 0.8 volts).
4
Check the exhaust system for leaks that could affect the O2 sensor readings.
5
Inspect the engine coolant temperature sensor to ensure it is functioning properly, as incorrect readings could lead to improper fuel mixture.
6
Clear the codes and perform a test drive to see if the P0138 code returns.

Solution

💡 Expert Tip

For complex repairs like this, consider taking photos at each step. This helps if you need to reverse a step or consult with a mechanic. Also, keep all removed parts organized - you may need to reference them during reassembly.

Verification

After completing the repair, verify that the issue has been resolved:

✓Test the affected component to ensure it functions correctly
✓Check for any error codes or warning lights
✓Monitor the vehicle for a few days to ensure the issue does not recur

Prevention Tips

To prevent this issue from occurring again:

•Follow the manufacturer's recommended maintenance schedule
•Address warning signs early before they develop into major issues
•Use quality parts and fluids recommended for your vehicle
•Keep detailed records of all repairs and maintenance

Tools & Equipment Required

•OBD-II scanner
•Oxygen sensor socket
•Ratchet
•Extension
•Multimeter

Parts Required

•Downstream oxygen sensor

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Diagnostic Steps

1
Scan for error codes using an OBD-II scanner to confirm P0138 and check for other related codes.
2
Inspect the wiring and connectors of the downstream oxygen sensor for any signs of damage, corrosion, or loose connections.
3
Measure the voltage output of the downstream O2 sensor using a multimeter to verify if it is consistently high (above 0.8 volts).
4
Check the exhaust system for leaks that could affect the O2 sensor readings.
5
Inspect the engine coolant temperature sensor to ensure it is functioning properly, as incorrect readings could lead to improper fuel mixture.
6
Clear the codes and perform a test drive to see if the P0138 code returns.

Solution

1. Preparation

Gather all necessary tools and parts.
Disconnect the battery to prevent electrical shorts.
Ensure the engine is cool before starting work.

2. Remove the Downstream O2 Sensor

Tools Required: Oxygen sensor socket, ratchet, and extension.
Locate the downstream oxygen sensor (after the catalytic converter).
Use the oxygen sensor socket to carefully unscrew the sensor from the exhaust pipe.
Disconnect the electrical connector from the sensor.

3. Inspect and Replace the Oxygen Sensor

Visually inspect the old sensor for signs of damage or excessive wear.
If the sensor appears faulty, install the new downstream O2 sensor:
- Apply anti-seize compound on the threads of the new sensor (if not pre-applied).
- Screw the new sensor into place by hand and then tighten it with the oxygen sensor socket to the manufacturer’s specified torque (usually around 30 lb-ft).
Reconnect the electrical connector securely.

4. Reconnect Battery and Clear Codes

Reconnect the negative battery terminal.
Use the OBD-II scanner to clear the P0138 code from the vehicle’s computer.

5. Test Drive and Monitor

Start the engine and let it idle for a few minutes.
Take the vehicle for a test drive under various conditions to allow the O2 sensor to begin functioning and be monitored by the ECU.