how to fix P0138 code in Ford Explorer Fifth Generation (2011-2019)

Ford Explorer Fifth Generation (2011-2019)

Error Codes

1-2 hours

Time

medium

Difficulty

medium

Severity

Error Code: P0138

3 min read

569 words

Problem Statement

Learn how to diagnose and fix P0138 oxygen sensor high voltage issue in Ford Explorer (2011-2019). Step-by-step guide with tools and procedures.

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 components.

Symptoms

•Check engine light illuminated
•Poor fuel economy
•Rough engine idle
•Increased emissions
•Possible engine stalling

Diagnostic Steps

1
Scan the vehicle's OBD-II system with a scanner to confirm the P0138 code and check for any additional codes.
2
Inspect the wiring and connectors leading to the Bank 1, Sensor 2 oxygen sensor for damage, corrosion, or loose connections.
3
Use a multimeter to measure the voltage output from the oxygen sensor; it should fluctuate between 0.1 to 0.9 volts.
4
Check the vehicle’s ground connections and ensure they are secure and free of corrosion.
5
Verify the fuel trim values using a scan tool to see if they are outside the normal range, which can indicate fuel delivery issues.
6
Inspect the exhaust system for any leaks that may affect the oxygen 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
•Oxygen sensor socket
•Torque wrench
•Basic hand tools (sockets, wrenches)

Parts Required

•New oxygen sensor (Bank 1, Sensor 2)

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Diagnostic Steps

1
Scan the vehicle's OBD-II system with a scanner to confirm the P0138 code and check for any additional codes.
2
Inspect the wiring and connectors leading to the Bank 1, Sensor 2 oxygen sensor for damage, corrosion, or loose connections.
3
Use a multimeter to measure the voltage output from the oxygen sensor; it should fluctuate between 0.1 to 0.9 volts.
4
Check the vehicle’s ground connections and ensure they are secure and free of corrosion.
5
Verify the fuel trim values using a scan tool to see if they are outside the normal range, which can indicate fuel delivery issues.
6
Inspect the exhaust system for any leaks that may affect the oxygen sensor readings.

Solution

1. Preparation

Gather all necessary tools and materials.
Disconnect the vehicle battery to prevent electrical shock.
Allow the engine to cool down completely.

2. Remove the Oxygen Sensor

Locate Bank 1, Sensor 2 oxygen sensor (usually located downstream of the catalytic converter).
Use an oxygen sensor socket to carefully unscrew and remove the old sensor.
Disconnect the wiring harness from the old sensor.

3. Inspect and Clean

Inspect the wiring harness for any frays or damage; repair as necessary.
Clean the threads of the oxygen sensor port on the exhaust system to remove any debris or carbon buildup.

4. Install New Oxygen Sensor

Apply anti-seize compound to the threads of the new oxygen sensor, avoiding the sensor tip.
Screw in the new oxygen sensor by hand, then tighten it using an oxygen sensor socket to the manufacturer’s specified torque (typically around 30 lb-ft).
Reconnect the wiring harness to the new oxygen sensor.

5. Reconnect Battery and Clear Codes

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

6. Test Drive

Start the engine and allow it to reach operating temperature.
Take the vehicle for a test drive to ensure the check engine light does not reappear.