AutoCodes – Ford – P1151 1997 Ford F150

P1151 1997 Ford F150 Code - Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 2

Quick Answer

The Heated Oxygen Sensor (HO2S) Monitor is an on-board strategy designed to monitor the HO2S sensors for a malfunction or deterioration that can affect emissions. Common causes include Faulty Upstream Oxygen Sensor Bank 2, Fuel pressure high or low, MAF sensor dirty/defective. 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: P1151 1997 Ford F150 indicates Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 2.
Common causes: Common causes include Faulty Upstream Oxygen Sensor Bank 2, Fuel pressure high or low, MAF sensor dirty/defective.
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 10,348

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 May 03, 2019

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P1151 1997 Ford F150 Description

The Heated Oxygen Sensor (HO2S) Monitor is an on-board strategy designed to monitor the HO2S sensors for a malfunction or deterioration that can affect emissions. Under specific conditions, the fuel control or upstream HO2S sensors are checked for proper output voltage and response rate (the time it takes to switch from lean to rich or rich to lean). Downstream HO2S sensors used for Catalyst Monitor are also monitored for proper output voltage. Input is required from the Engine Coolant Temperature (ECT) or Cylinder Head Temperature (CHT), Inlet Air Temperature (IAT), Mass Air Flow (MAF), Throttle Position (TP) and Crankshaft Position (CKP) sensors to activate the HO2S Monitor. The Fuel System Monitor and Misfire Detection Monitor must also have completed successfully before the HO2S Monitor is enabled.
• The HO2S sensor senses the oxygen content in the exhaust flow and outputs a voltage between zero and 1.0 volt. Lean of stoichiometric (air/fuel ratio of approximately 14.7:1 for gasoline engines), the HO2S will generate a voltage between zero and 0.45 volt. Rich of stoichiometric, the HO2S will generate a voltage between 0.45 and 1.0 volt.
• The HO2S Monitor evaluates both the upstream (Fuel Control) and downstream (Catalyst Monitor) HO2S for proper function.
• Once the HO2S Monitor is enabled, the upstream HO2S signal voltage amplitude and response frequency are checked. Excessive voltage is determined by comparing the HO2S signal voltage to a maximum calibratable threshold voltage.
• A fixed frequency closed loop fuel control routine is executed and the upstream HO2S voltage amplitude and output response frequency are observed. A sample of the upstream HO2S signal is evaluated to determine if the sensor is capable of switching or has a slow response rate.
• An HO2S heater circuit fault is determined by turning the heater on and off and looking for a corresponding change in the OSM and by
measuring the current going through the heater circuit.
• The MIL is activated after a fault is detected on two consecutive OBD II drive cycles.

OBDII Code P1151 1997 Ford F150 - Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 2 - AutoCodes.com — P1151 1997 Ford F150 Code - Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 2

What does this mean?

What are the Possible Causes of the DTC P1151 1997 Ford F150?

Faulty Upstream Oxygen Sensor Bank 2
Fuel pressure high or low
MAF sensor dirty/defective
Vacuum leak on engine
Leaking fuel injector or fuel pressure regulator
Faulty Powertrain Control Module (PCM)

How to Fix the DTC P1151 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

The code means that the Powertrain Control Module (PCM) has detected a lean system, which means that there is either not enough fuel or and excessive amount of air in the system. Start by checking for vacuum leaks.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P1151 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 P1151 1997 Ford F150 code?

Need more information on how to fix the P1151 1997 Ford F150 code? Get Access to Factory Service Manuals

Need Help with the 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 P1151 1997 Ford F150 Code

1. What are the common symptoms of OBDII code P1151 in a 1997 Ford F150?

- Common symptoms include poor fuel economy, rough idling, hesitation during acceleration, and potential stalling.

2. What does the OBDII code P1151 in a 1997 Ford F150 indicate?

- The code indicates a lack of activity in the upstream heated oxygen sensor on bank 2, suggesting a lean air-fuel mixture.

3. What are the possible causes of OBDII code P1151 in a 1997 Ford F150?

- Common causes include a faulty oxygen sensor, vacuum leaks, fuel system issues, exhaust leaks, or a problem with the engine's air intake system.

4. How can I diagnose the OBDII code P1151 in my 1997 Ford F150?

- Diagnosing this code typically involves checking the oxygen sensor's wiring, inspecting for vacuum leaks, testing the fuel pressure, and examining the exhaust system for leaks.

5. What are some repair tips for resolving OBDII code P1151 in a 1997 Ford F150?

- Repair tips may include replacing the upstream oxygen sensor, fixing any vacuum leaks, addressing fuel system issues, and repairing exhaust leaks.

6. Can I continue driving my 1997 Ford F150 with OBDII code P1151?

- 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.

7. How much does it typically cost to repair OBDII code P1151 in a 1997 Ford F150?

- The cost of repair can vary depending on the specific issue causing the code, but it may range from $100 for a simple fix to several hundred dollars for more extensive repairs.

8. Will resetting the OBDII code P1151 in my 1997 Ford F150 make it go away permanently?

- Resetting the code may temporarily turn off the check engine light, but if the underlying issue is not fixed, the code is likely to return.

9. How long does it take to repair OBDII code P1151 in a 1997 Ford F150?

- The repair time can vary depending on the exact cause of the code, but it may take anywhere from 1-3 hours to diagnose and fix the issue.

10. Can a DIY enthusiast fix OBDII code P1151 in a 1997 Ford F150?

- Depending on the skill level and tools available, some DIY enthusiasts may be able to address simpler causes like replacing the oxygen sensor, but more complex issues may require professional help.