how to fix code P0138 in Honda CR-V Fifth Generation (2017-2022)

Honda CR-V 6th Gen (2023-Present)

Error Codes

1-2 hours

Time

medium

Difficulty

medium

Severity

Error Code: P0138

3 min read

524 words

Problem Statement

Learn how to diagnose and fix P0138 high voltage signal from the upstream oxygen sensor in Honda CR-V 2017-2022. Step-by-step guide included.

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 working on the exhaust system to avoid burns.

Symptoms

•Check engine light illuminated
•Decreased fuel economy
•Engine running rich (excess fuel)
•Rough idle or engine stalling
•Increased emissions during emissions testing

Diagnostic Steps

1
Scan for error codes using an OBD-II scanner to confirm P0138 and check for any related codes.
2
Inspect the wiring and connectors of the upstream oxygen sensor for damage, corrosion, or loose connections.
3
Test the voltage output of the upstream oxygen sensor using a multimeter while the engine is running.
4
Check the engine coolant temperature (ECT) sensor to ensure it is functioning correctly, as it can affect O2 sensor readings.
5
Inspect for exhaust leaks before the O2 sensor, which could cause incorrect readings.
6
Verify the fuel pressure to ensure it’s within specifications, as excessive fuel pressure can lead to a rich condition.

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

•New upstream oxygen sensor

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Diagnostic Steps

1
Scan for error codes using an OBD-II scanner to confirm P0138 and check for any related codes.
2
Inspect the wiring and connectors of the upstream oxygen sensor for damage, corrosion, or loose connections.
3
Test the voltage output of the upstream oxygen sensor using a multimeter while the engine is running.
4
Check the engine coolant temperature (ECT) sensor to ensure it is functioning correctly, as it can affect O2 sensor readings.
5
Inspect for exhaust leaks before the O2 sensor, which could cause incorrect readings.
6
Verify the fuel pressure to ensure it’s within specifications, as excessive fuel pressure can lead to a rich condition.

Solution

1. Preparation

Gather necessary tools and parts.
Disconnect the vehicle battery to ensure safety.

Tools Required:

OBD-II scanner
Multimeter
Socket set
Torque wrench
Oxygen sensor socket
Safety goggles
Gloves

2. Inspect and Repair Wiring

Inspect Wiring:
- Check the O2 sensor wiring harness for frays, cuts, or corrosion.
- If damage is found, repair or replace the affected wiring.
Check Connectors:
- Ensure that the connectors are clean and secure. Clean with electrical contact cleaner if corroded.

3. Replace Upstream Oxygen Sensor

Remove Old Sensor:
- Use the oxygen sensor socket to unscrew the old sensor from the exhaust manifold.
- Disconnect the wiring harness from the sensor.
Install New Sensor:
- Apply anti-seize compound to the threads of the new O2 sensor.
- Screw in the new sensor and torque it to the manufacturer’s specifications (typically around 30 lb-ft).
- Reconnect the wiring harness securely.

4. Reset the Check Engine Light

Use the OBD-II scanner to clear the P0138 code from the vehicle's computer.
Reconnect the battery if it was disconnected.