how to fix the P0138 code on my Toyota Highlander Third Generation (2014-2019)

Toyota Highlander Third Generation (2014-2019)

Error Codes

1-2 hours

Time

medium

Difficulty

medium

Severity

Error Code: P0138

3 min read

500 words

Problem Statement

Learn how to diagnose and fix P0138 oxygen sensor issue in Toyota Highlander. 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 starting any repairs to prevent burns.

Symptoms

•Check engine light illuminated
•Decreased fuel efficiency
•Rough engine idle
•Poor acceleration
•Increased emissions
•Failed emissions test

Diagnostic Steps

1
Scan the vehicle's onboard diagnostic system using an OBD-II scanner to confirm the P0138 code and check for any additional codes.
2
Inspect the wiring and connectors leading to Bank 1 Sensor 2 for any signs of damage, corrosion, or loose connections.
3
Measure the voltage output of the oxygen sensor using a multimeter to determine if it is functioning correctly.
4
Check the vehicle's exhaust system for leaks that could affect sensor readings.
5
Inspect the engine coolant temperature sensor for proper operation, as incorrect readings can affect fuel mixture and sensor performance.
6
Clear the codes and take the vehicle for a test drive to see if the code returns, confirming the issue.

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
•Oxygen sensor socket
•Socket wrench set
•Torque wrench

Parts Required

•New oxygen sensor (Bank 1 Sensor 2)

Related Faults

Share this solution

Comments

No comments yet

Be the first to share your thoughts

Back to Generation

Diagnostic Steps

1
Scan the vehicle's onboard diagnostic system using an OBD-II scanner to confirm the P0138 code and check for any additional codes.
2
Inspect the wiring and connectors leading to Bank 1 Sensor 2 for any signs of damage, corrosion, or loose connections.
3
Measure the voltage output of the oxygen sensor using a multimeter to determine if it is functioning correctly.
4
Check the vehicle's exhaust system for leaks that could affect sensor readings.
5
Inspect the engine coolant temperature sensor for proper operation, as incorrect readings can affect fuel mixture and sensor performance.
6
Clear the codes and take the vehicle for a test drive to see if the code returns, confirming the issue.

Solution

1. Preparation

Gather necessary tools and parts.
Disconnect the battery to ensure safety.
Ensure the vehicle is on a level surface and secure it with jack stands if needed.

2. Remove the Oxygen Sensor

Locate Bank 1 Sensor 2 (typically found downstream of the catalytic converter).
Use a socket wrench to carefully unscrew the oxygen sensor from its mounting location.
Disconnect the wiring harness connected to the sensor.

3. Inspect and Replace the Oxygen Sensor

Visually inspect the old sensor for signs of carbon buildup or damage.
If the sensor appears faulty, replace it with a new, compatible oxygen sensor.
Ensure the new sensor has the correct part number for your vehicle model.

4. Reinstallation

Reconnect the wiring harness to the new oxygen sensor.
Screw the new sensor into place and tighten it to the manufacturer's specifications (usually around 30-40 Nm).
Reconnect the battery.

5. Final Checks

Start the engine and let it idle, checking for any exhaust leaks around the oxygen sensor.
Monitor the engine's performance and ensure no warning lights remain illuminated.