AutoCodes – Ford – P1138 Ford

P1138 Ford Code - Lack Of Heated Oxygen Sensor Switches Bank 1 Sensor 2 Switch Indicates Rich

Quick Answer

The Heated Oxygen Sensor 2 (HO2S2) (Downstream), after the three-way catalyst (manifold), monitors the oxygen level in the exhaust gas on each bank. Common causes include Exhaust gas leaks, Faulty Heated Oxygen Sensor 2 (HO2S2) (Downstream) Bank 1, Heated Oxygen Sensor 2 Bank 1 harness is open or shorted. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: P1138 Ford indicates Lack Of Heated Oxygen Sensor Switches Bank 1 Sensor 2 Switch Indicates Rich.
Common causes: Common causes include Exhaust gas leaks, Faulty Heated Oxygen Sensor 2 (HO2S2) (Downstream) Bank 1, Heated Oxygen Sensor 2 Bank 1 harness is open or shorted.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 17,815

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Intermediate (2 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jul 24, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P1138 Ford Description

The Heated Oxygen Sensor 2 (HO2S2) (Downstream), after the 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 maintain near the ideal stoichiometric ratio. The HO2S2 output voltage changes suddenly in the vicinity of the stoichiometric ratio. The Powertrain Control Module (PCM) adjusts the fuel injection time so that the air-fuel ratio is nearly stoichiometric. The HO2S2 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 PCM interprets Lean when the HO2S2 voltage is below 0.45 V. If the oxygen in the exhaust gas decreases, the air-fuel ratio becomes Rich. The PCM interprets Rich when the HO2S2 voltage is above 0.45 V. The P1138 code will set when the PCM detects that the HO2S2 signal is above the voltage of range for an extended period.

OBDII Code P1138 Ford - Lack Of Heated Oxygen Sensor Switches Bank 1 Sensor 2 Switch Indicates Rich - AutoCodes.com — P1138 Ford Code - Lack Of Heated Oxygen Sensor Switches Bank 1 Sensor 2 Switch Indicates Rich

What does this mean?

What are the Possible Causes of the DTC P1138 Ford?

Exhaust gas leaks
Faulty Heated Oxygen Sensor 2 (HO2S2) (Downstream) Bank 1
Heated Oxygen Sensor 2 Bank 1 harness is open or shorted
Heated Oxygen Sensor 2 Bank 1 circuit poor electrical connection
Inappropriate fuel pressure
Faulty fuel injectors

How to Fix the DTC P1138 Ford?

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 is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P1138 Ford 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 P1138 Ford code?

Need more information on how to fix the P1138 Ford code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P1138 Ford code diagnosed by a professional: Find a repair shop in your area

Information for Specific Ford Models

P1138 1997 Ford F150 — Lack Of Heated Oxygen Sensor Switches Bank 1 Sensor 2 Switch Indicates Rich
P1138 1998 Ford F150 — Lack Of Heated Oxygen Sensor Switches Bank 1 Sensor 2 Switch Indicates Rich
P1138 1999 Ford F150 — Lack Of Heated Oxygen Sensor Switches Bank 1 Sensor 2 Switch Indicates Rich
P1138 2000 Ford F150 — Lack Of Heated Oxygen Sensor Switches Bank 1 Sensor 2 Switch Indicates Rich
P1138 2001 Ford F150 — Lack Of Heated Oxygen Sensor Switches Bank 1 Sensor 2 Switch Indicates Rich
P1138 2002 Ford F150 — Lack Of Heated Oxygen Sensor Switches Bank 1 Sensor 2 Switch Indicates Rich
P1138 2003 Ford F150 — Lack Of Heated Oxygen Sensor Switches Bank 1 Sensor 2 Switch Indicates Rich

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 P1138 Ford Code

1. What are common symptoms of OBDII code P1138 in a Ford vehicle?

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

2. What does the OBDII code P1138 'Lack Of Heated Oxygen Sensor Switches Bank 1 Sensor 2 Switch Indicates Rich' mean in a Ford?

- This code indicates that the heated oxygen sensor for bank 1 sensor 2 is detecting a rich air-fuel mixture in the exhaust.

3. What are possible causes of OBDII code P1138 in a Ford?

- Possible causes include a faulty oxygen sensor, issues with the fuel system, vacuum leaks, exhaust leaks, or a malfunctioning engine coolant temperature sensor.

4. How can I diagnose the cause of OBDII code P1138 in my Ford?

- Diagnosing this code may involve checking the oxygen sensor's operation, inspecting for leaks in the exhaust system, testing the fuel system components, and scanning for other related trouble codes.

5. Can driving with OBDII code P1138 in a Ford cause further damage?

- Driving with this code may lead to decreased fuel efficiency and potential damage to the catalytic converter over time if not addressed promptly.

6. How can I repair OBDII code P1138 in a Ford?

- Repair options may include replacing the faulty oxygen sensor, fixing any leaks in the exhaust system, addressing issues with the fuel system, or repairing faulty engine sensors.

7. Is it safe to continue driving my Ford with OBDII code P1138 present?

- It is generally not recommended to continue driving with this code as it can affect the vehicle's performance and fuel efficiency. It's best to address the issue promptly.

8. Can I reset OBDII code P1138 in my Ford without fixing the underlying issue?

- While you can clear the code with an OBDII scanner, it will likely reappear if the underlying issue is not resolved. It's important to address the root cause of the problem.

9. How much does it typically cost to repair OBDII code P1138 in a Ford?

- The cost of repairs can vary depending on the specific issue causing the code. Costs may include parts and labor for replacing sensors, fixing leaks, or addressing fuel system problems.

10. Can a DIY enthusiast fix OBDII code P1138 in a Ford?

- Depending on the skill level and experience of the DIY enthusiast, some repairs related to this code, such as replacing an oxygen sensor, may be feasible. However, more complex issues may require professional assistance.