AutoCodes – Ford – P0138 2003 Ford F150

P0138 2003 Ford F150 Code - O2 Sensor Circuit High Voltage Bank 1 Sensor 2

Quick Answer

The Heated Oxygen Sensor 2 (HO2S) (Rear O2 Sensor), after three way catalyst (manifold), monitors the oxygen level in the exhaust gas on each bank. Common causes include Faulty Rear Heated Oxygen Sensor Bank 1, Rear Heated Oxygen Sensor Bank 1 harness is open or shorted, Rear Heated Oxygen Sensor Bank 1 circuit poor electrical connection. Severity is Moderate - service should be scheduled soon. The vehicle may still be drivable for short trips if it runs normally, but avoid hard driving and repair it soon.

What it means: P0138 2003 Ford F150 indicates O2 Sensor Circuit High Voltage Bank 1 Sensor 2.
Common causes: Common causes include Faulty Rear Heated Oxygen Sensor Bank 1, Rear Heated Oxygen Sensor Bank 1 harness is open or shorted, Rear Heated Oxygen Sensor Bank 1 circuit poor electrical connection.
Severity: Moderate - service should be scheduled soon.
Can I drive?: The vehicle may still be drivable for short trips if it runs normally, but avoid hard driving and repair it soon.

Save to My Repairs Step-by-Step Diagnostic Guide My Repairs

AI answers can be wrong. Verify repairs with testing. Open full chat

Code Popularity 6,107

How popular is this code, among other codes? Low

Repair Importance Level

Moderate (Service soon) (2 / 3)

Repair Difficulty Level

Intermediate (2 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jun 14, 2020

Description
Step-by-Step Diagnostic Guide
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
Add Comment

💬 Need more help? Ask Coddy for instant answers — it's free!

Code P0138 2003 Ford F150 Description

The Heated Oxygen Sensor 2 (HO2S) (Rear O2 Sensor), after three way catalyst (manifold), monitors the oxygen level in the exhaust gas on each bank. For optimum catalyst operation, the air fuel mixture (air-fuel ratio) must be maintained near the ideal stoichiometric ratio. The HO2S output voltage changes suddenly in the vicinity of the stoichiometric ratio. The Engine Control Module (ECM) adjusts the fuel injection time so that the air-fuel ratio is nearly stoichiometric. The HO2S generates a voltage between 0.1 and 0.9 V in response to oxygen in the exhaust gas. If the oxygen in the exhaust gas increases, the air-fuel ratio becomes Lean. The ECM interprets Lean when the HO2S voltage is below 0.45 V. If the oxygen in the exhaust gas decreases, the air-fuel ratio becomes Rich. The ECM interprets Rich when the HO2S voltage is above 0.45 V.

OBDII Code P0138 2003 Ford F150 - O2 Sensor Circuit High Voltage Bank 1 Sensor 2 - AutoCodes.com — P0138 2003 Ford F150 Code - O2 Sensor Circuit High Voltage Bank 1 Sensor 2

What does this mean?

What are the Possible Causes of the DTC P0138 2003 Ford F150?

Faulty Rear Heated Oxygen Sensor Bank 1
Rear Heated Oxygen Sensor Bank 1 harness is open or shorted
Rear Heated Oxygen Sensor Bank 1 circuit poor electrical connection
Intake air leaks
Exhaust gas leaks
Inappropriate fuel pressure
Faulty fuel injectors

How to Fix the DTC P0138 2003 Ford F150?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What does this mean?

Code Tech Notes

Replacing the Rear Heated Oxygen Sensor Bank 1 usually takes care of the problem.
The HO2S Sensor Signals are monitored for an over voltage fault. The code is set when HO2S signal voltage is 1.5 volts or greater.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0138 2003 Ford F150 code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the P0138 2003 Ford F150 code?

Need more information on how to fix the P0138 2003 Ford F150 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P0138 2003 Ford F150 code diagnosed by a professional: Find a repair shop in your area

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P0138 2003 Ford F150 Code

1. What are the common symptoms of OBDII code P0138 on a 2003 Ford F150?

- Common symptoms include poor fuel economy, rough idling, engine misfires, and the illumination of the Check Engine Light.

2. What does the OBDII code P0138 "O2 Sensor Circuit High Voltage Bank 1 Sensor 2" mean for a 2003 Ford F150?

- This code indicates that the downstream oxygen sensor in bank 1 is detecting a voltage higher than normal, possibly due to an issue with the sensor or its wiring.

3. What are the possible causes of OBDII code P0138 on a 2003 Ford F150?

- The causes can include a faulty oxygen sensor, damaged wiring or connectors, exhaust leaks, engine misfires, or issues with the engine's computer.

4. How can I diagnose the O2 sensor circuit high voltage issue on Bank 1 Sensor 2 in a 2003 Ford F150?

- You can use a multimeter to test the voltage output of the oxygen sensor, inspect the wiring for any damage, and check for exhaust leaks that could affect sensor readings.

5. Can I still drive my 2003 Ford F150 with OBDII code P0138 present?

- It is generally safe to drive the vehicle for a short period with this code, but it is recommended to address the issue promptly to prevent potential damage to the catalytic converter.

6. How do I repair OBDII code P0138 on a 2003 Ford F150?

- Repair options may include replacing the downstream oxygen sensor, repairing or replacing damaged wiring, fixing exhaust leaks, addressing engine misfires, or resetting the engine control module.

7. Are there any DIY tips for fixing the O2 sensor circuit high voltage issue in a 2003 Ford F150?

- DIY enthusiasts can start by inspecting the sensor wiring and connectors for damage, ensuring a secure connection, and checking for any visible exhaust leaks near the sensor.

8. Can a dirty or contaminated oxygen sensor cause OBDII code P0138 on a 2003 Ford F150?

- Yes, a dirty or contaminated oxygen sensor can lead to incorrect voltage readings, triggering the P0138 code. Cleaning or replacing the sensor may resolve the issue.

9. How soon should I address OBDII code P0138 on my 2003 Ford F150?

- It is recommended to address this code as soon as possible to prevent potential damage to the catalytic converter and ensure optimal engine performance and fuel efficiency.

10. Will resetting the Check Engine Light make OBDII code P0138 go away on a 2003 Ford F150?

- Resetting the Check Engine Light may temporarily turn it off, but if the underlying issue causing code P0138 is not resolved, the light is likely to come back on after a short period.