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

Honda Civic 11th Generation (2022-Present)

Error Codes

2-4 hours

Time

medium

Difficulty

medium

Severity

Error Code: P0138

3 min read

550 words

Problem Statement

Learn how to diagnose and fix P0138 high voltage from the oxygen sensor in Honda Civic 10th Generation. Step-by-step guide with tools and procedures.

Error Code

P0138

Affected Component

Exhaust System

Estimated Time

2-4 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 avoid burns.

Symptoms

•Check engine light illuminated
•Poor fuel economy
•Rough engine idle
•Increased emissions
•Engine stalling or hesitation during acceleration

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 leading to the downstream O2 sensor for any signs of damage or corrosion.
3
Measure the voltage output of the downstream O2 sensor with a multimeter while the engine is running.
4
Check the vehicle's fuel trim values using a scan tool to see if they are outside normal parameters.
5
Inspect the exhaust system for any leaks that could affect O2 sensor readings.

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
•Multimeter
•Socket set
•Torque wrench
•Oxygen sensor socket
•Safety goggles
•Gloves

Parts Required

•Downstream oxygen sensor (if faulty)

Related Faults

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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 leading to the downstream O2 sensor for any signs of damage or corrosion.
3
Measure the voltage output of the downstream O2 sensor with a multimeter while the engine is running.
4
Check the vehicle's fuel trim values using a scan tool to see if they are outside normal parameters.
5
Inspect the exhaust system for any leaks that could affect O2 sensor readings.

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.