What does error code P0138 indicate for the 2020 Ford Explorer?

Ford Explorer Sixth Generation (2020-present)

Error Codes

2-3 hours

Time

medium

Difficulty

medium

Severity

Error Code: P0138

3 min read

549 words

Problem Statement

Learn how to diagnose and repair error code P0138 related to the oxygen sensor circuit in the 2020 Ford Explorer. Follow our step-by-step guide.

Error Code

P0138

Affected Component

Oxygen Sensor Circuit

Estimated Time

2-3 hours

Symptoms

•Check Engine Light (CEL) illuminated
•Decreased fuel efficiency
•Rough idling
•Failed emissions test
•Poor engine performance or hesitation during acceleration

Diagnostic Steps

1
Verify the presence of the P0138 code using an OBD-II scanner.
2
Inspect the wiring and connectors leading to the Bank 1, Sensor 2 oxygen sensor for signs of damage, corrosion, or disconnection.
3
Use a multimeter to measure the voltage output of the Bank 1, Sensor 2 oxygen sensor.
4
Disconnect the oxygen sensor connector and check for a short to voltage on the wiring harness.
5
Check for any software updates or known issues with the ECM.

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
•Basic hand tools (screwdrivers, socket set, etc.)
•Wiring diagram for the vehicle

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Diagnostic Steps

1
Verify the presence of the P0138 code using an OBD-II scanner.
2
Inspect the wiring and connectors leading to the Bank 1, Sensor 2 oxygen sensor for signs of damage, corrosion, or disconnection.
3
Use a multimeter to measure the voltage output of the Bank 1, Sensor 2 oxygen sensor.
4
Disconnect the oxygen sensor connector and check for a short to voltage on the wiring harness.
5
Check for any software updates or known issues with the ECM.

Solution

Error Code P0138: Overview

The error code P0138 indicates a problem with the Oxygen Sensor Circuit High Voltage (Bank 1, Sensor 2). This code suggests that the engine control module (ECM) is detecting a voltage level that is higher than expected from the oxygen sensor located after the catalytic converter (Bank 1, Sensor 2).

Tools Required

OBD-II Scanner
Multimeter
Basic hand tools (screwdrivers, socket set, etc.)
Wiring diagram for the vehicle (for reference)

Repair Instructions

Replace Oxygen Sensor (If Faulty)
- If testing indicates the oxygen sensor is faulty, proceed with replacement:
  1. Locate the Bank 1, Sensor 2 oxygen sensor (usually located in the exhaust pipe after the catalytic converter).
  2. Disconnect the sensor's electrical connector.
  3. Use an oxygen sensor socket or wrench to remove the sensor from the exhaust pipe.
  4. Install the new oxygen sensor, ensuring to use anti-seize compound on the threads (if applicable).
  5. Reconnect the electrical connector and ensure it is secure.
Repair Wiring Issues (If Present)
- If any damaged wiring or connectors are found during inspection:
  1. Repair or replace damaged wiring.
  2. Ensure all connections are clean and secure.
Clear Codes and Test Drive
- Once repairs are complete:
  1. Use the OBD-II scanner to clear the codes from the ECM.
  2. Take the vehicle for a test drive to ensure the issue is resolved and the Check Engine Light does not reappear.
Final Check
- After the test drive, re-scan the vehicle for DTCs to confirm that P0138 has not returned.

Conclusion

Following these steps should help diagnose and resolve the P0138 error code on a 2020 Ford Explorer. If issues persist after following the repair instructions, further diagnosis may be necessary, potentially involving the ECM or deeper electrical system issues.