AutoCodes – Ford – P1138 1998 Ford F150

P1138 1998 Ford F150 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 1998 Ford F150 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 2,950

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 1998 Ford F150 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 1998 Ford F150 - Lack Of Heated Oxygen Sensor Switches Bank 1 Sensor 2 Switch Indicates Rich - AutoCodes.com — P1138 1998 Ford F150 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 1998 Ford F150?

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 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 is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P1138 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 P1138 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 P1138 1998 Ford F150 Code

1. What are the common symptoms of OBDII code P1138 in a 1998 Ford F150?

- Common symptoms include decreased fuel economy, rough idling, and potential engine misfires.

2. What does the OBDII code P1138 indicating "Lack Of Heated Oxygen Sensor Switches Bank 1 Sensor 2 Switch Indicates Rich" mean?

- This code indicates that the downstream oxygen sensor on Bank 1 is detecting a consistently rich air-fuel mixture.

3. What are the potential causes of OBDII code P1138 in a 1998 Ford F150?

- Possible causes include a faulty oxygen sensor, a vacuum leak, a malfunctioning fuel injector, or issues with the engine's air intake system.

4. How can I diagnose the underlying issue causing OBDII code P1138 in my 1998 Ford F150?

- You can use a scan tool to monitor sensor data, perform a visual inspection for any visible damage or leaks, and conduct a smoke test to check for vacuum leaks.

5. Can a dirty or clogged air filter trigger OBDII code P1138 in a 1998 Ford F150?

- Yes, a dirty or clogged air filter can disrupt the air-fuel mixture ratio and potentially lead to a rich condition detected by the oxygen sensor.

6. What are some repair tips for addressing OBDII code P1138 in a 1998 Ford F150?

- Start by checking and replacing the downstream oxygen sensor if needed, inspecting and repairing any vacuum leaks, and ensuring proper operation of fuel injectors.

7. Is it safe to continue driving with OBDII code P1138 present in a 1998 Ford F150?

- It is not recommended to drive with this code unresolved, as it can lead to poor engine performance and potentially cause damage to the catalytic converter.

8. Can a malfunctioning catalytic converter trigger OBDII code P1138 in a 1998 Ford F150?

- Yes, a faulty catalytic converter can impact the readings from the oxygen sensor and contribute to a rich air-fuel mixture condition.

9. How much does it typically cost to repair OBDII code P1138 in a 1998 Ford F150?

- The cost of repair can vary depending on the exact cause of the issue, but it may range from $100 to $500 or more, including parts and labor.

10. How can I prevent OBDII code P1138 from recurring in my 1998 Ford F150?

- Regular maintenance, such as replacing the oxygen sensors at recommended intervals, keeping the air filter clean, and addressing any engine issues promptly, can help prevent the code from reappearing.