AutoCodes – Ford – P0138 1998 Ford F150

P0138 1998 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 1998 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 2,628

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 1998 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 1998 Ford F150 - O2 Sensor Circuit High Voltage Bank 1 Sensor 2 - AutoCodes.com — P0138 1998 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 1998 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 1998 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 1998 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 1998 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 1998 Ford F150 Code

1. What are the common symptoms of OBDII code P0138 in a 1998 Ford F150?

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

2. What does the OBDII code P0138 on a 1998 Ford F150 indicate?

- The code P0138 indicates a high voltage condition in the O2 sensor circuit of Bank 1 Sensor 2 in the exhaust system.

3. What are the possible causes of OBDII code P0138 in a 1998 Ford F150?

- Possible causes include a faulty O2 sensor, wiring issues, exhaust leaks, engine misfires, or a malfunctioning PCM (Powertrain Control Module).

4. How can I diagnose and repair OBDII code P0138 on my 1998 Ford F150?

- Start by inspecting the O2 sensor wiring for any damage or corrosion. Check for exhaust leaks and ensure proper sensor operation. If necessary, replace the O2 sensor or repair the wiring connections.

5. Can a dirty or contaminated O2 sensor trigger code P0138 on a 1998 Ford F150?

- Yes, a dirty or contaminated O2 sensor can cause erratic readings and trigger a high voltage condition, leading to the activation of code P0138.

6. Is it safe to continue driving my 1998 Ford F150 with OBDII code P0138 present?

- It is not recommended to drive with code P0138 present, as it can lead to decreased fuel efficiency, engine performance issues, and potential damage to the catalytic converter over time.

7. How do I reset the Check Engine Light after repairing OBDII code P0138 on my 1998 Ford F150?

- You can reset the Check Engine Light using an OBDII scanner. Once the repair is completed, clear the trouble codes and monitor the system for any recurrence of the issue.

8. Will replacing the O2 sensor fix OBDII code P0138 in a 1998 Ford F150?

- In many cases, replacing a faulty O2 sensor can resolve code P0138. However, it is essential to ensure proper diagnosis and address any underlying wiring or exhaust issues.

9. How long does it take to repair OBDII code P0138 on a 1998 Ford F150?

- The repair time for code P0138 can vary depending on the exact cause and the complexity of the repair. It may take anywhere from 30 minutes to a few hours to complete the repair.

10. Can a DIY enthusiast tackle the repair of OBDII code P0138 on a 1998 Ford F150?

- Yes, with the right tools and knowledge, a DIY enthusiast can diagnose and repair code P0138. However, if unsure, it is recommended to seek professional help to ensure the issue is resolved correctly.