AutoCodes – Ford – P0138 1997 Ford F150

P0138 1997 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 1997 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.

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Code Popularity 2,919

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
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Code P0138 1997 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 1997 Ford F150 - O2 Sensor Circuit High Voltage Bank 1 Sensor 2 - AutoCodes.com — P0138 1997 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 1997 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 1997 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 1997 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 1997 Ford F150 code?

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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 1997 Ford F150 Code

1. What are the common symptoms of OBDII code P0138 on a 1997 Ford F150?

- Common symptoms include poor fuel economy, rough idling, engine misfires, and the illumination of the check engine light.

2. What does the O2 Sensor Circuit High Voltage Bank 1 Sensor 2 mean for a 1997 Ford F150?

- This code indicates that the downstream oxygen sensor in bank 1 (cylinder 1 side) is detecting a higher than normal voltage.

3. What are the possible causes of OBDII code P0138 on a 1997 Ford F150?

- Potential causes include a faulty oxygen sensor, wiring issues in the sensor circuit, exhaust leaks, engine misfires, or a malfunctioning engine control module.

4. How can I diagnose and repair OBDII code P0138 on my 1997 Ford F150?

- To diagnose this code, you can use a scan tool to check the oxygen sensor readings and inspect the sensor's wiring for any damage. Repair involves replacing the faulty oxygen sensor or addressing any wiring issues.

5. Can I drive my 1997 Ford F150 with OBDII code P0138?

- It is generally safe to drive the vehicle for a short period with this code, but prolonged driving can lead to decreased fuel efficiency and potential damage to the catalytic converter.

6. How much does it cost to repair OBDII code P0138 on a 1997 Ford F150?

- The cost of repairing this code can vary depending on the underlying issue. Replacing a faulty oxygen sensor can range from $100 to $300, while addressing wiring problems or other issues may increase the cost.

7. What happens if I ignore OBDII code P0138 on my 1997 Ford F150?

- Ignoring this code can lead to reduced fuel efficiency, engine performance issues, and potential damage to the catalytic converter over time.

8. Can a DIY enthusiast fix OBDII code P0138 on a 1997 Ford F150?

- Yes, a DIY enthusiast with the necessary tools and knowledge can typically replace the oxygen sensor or address wiring issues causing this code.

9. How often should the oxygen sensors be replaced on a 1997 Ford F150 to avoid OBDII code P0138?

- Oxygen sensors generally have a lifespan of around 60,000 to 100,000 miles. Regularly inspecting and replacing them at the recommended intervals can help prevent issues like code P0138.

10. Will resetting the check engine light resolve OBDII code P0138 on a 1997 Ford F150?

- Resetting the check engine light will only clear the code temporarily. To address the underlying issue causing code P0138, proper diagnosis and repair are necessary.