AutoCodes – Ford – P0138 2002 Ford F150

P0138 2002 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 2002 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 4,650

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 2002 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 2002 Ford F150 - O2 Sensor Circuit High Voltage Bank 1 Sensor 2 - AutoCodes.com — P0138 2002 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 2002 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 2002 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 2002 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 2002 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 2002 Ford F150 Code

1. What are the common symptoms of OBDII code P0138 on a 2002 Ford F150?

- Common symptoms include poor fuel economy, rough idling, engine hesitation, and potential loss of power.

2. What does the OBDII code P0138 indicate on a 2002 Ford F150?

- The code P0138 specifically points to an issue with the O2 sensor circuit high voltage for Bank 1 Sensor 2 in the vehicle's exhaust system.

3. What are the possible causes of the O2 sensor circuit high voltage fault on Bank 1 Sensor 2 in a 2002 Ford F150?

- Common causes include a faulty O2 sensor, damaged wiring or connectors, exhaust leaks, or issues with the vehicle's engine control module (ECM).

4. How can I diagnose the O2 sensor circuit high voltage issue on Bank 1 Sensor 2 in my 2002 Ford F150?

- Use a scan tool to read and clear the trouble code, inspect the O2 sensor and its wiring for any damage, and check for exhaust leaks near the sensor.

5. Can I continue driving my 2002 Ford F150 with the P0138 code?

- It is not recommended to continue driving with the P0138 code as it can lead to decreased fuel efficiency and potential damage to the catalytic converter.

6. How do I repair the O2 sensor circuit high voltage fault on Bank 1 Sensor 2 in my 2002 Ford F150?

- Repair options include replacing the faulty O2 sensor, repairing damaged wiring or connectors, fixing any exhaust leaks, or resetting the ECM.

7. Is it possible to reset the OBDII code P0138 on a 2002 Ford F150 without fixing the underlying issue?

- While you can clear the code using a scan tool, it is essential to address the root cause of the problem to prevent it from reoccurring.

8. Can a dirty air filter cause the O2 sensor circuit high voltage fault on a 2002 Ford F150?

- A dirty air filter is unlikely to directly cause the P0138 code, but it can impact overall engine performance and fuel efficiency, so it's still important to maintain a clean air filter.

9. How much does it cost to replace an O2 sensor on a 2002 Ford F150?

- The cost of replacing an O2 sensor can vary depending on the brand, location, and whether you choose to do it yourself or have a professional mechanic perform the replacement.

10. Will driving at high speeds affect the O2 sensor circuit high voltage fault on a 2002 Ford F150?

- Driving at high speeds may not directly affect the O2 sensor circuit fault, but it's important to address the issue promptly to prevent any further damage to the vehicle's systems.