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Engine-Codes – Ford – P0171 1999 Ford F150

P0171 1999 Ford F150 Code - Fuel Injection System Too Lean Bank 1

Quick Answer

The P0171 code on a 1999 Ford F150 indicates that the fuel injection system on bank 1 is operating too lean. Common causes include Vacuum leak, Faulty oxygen sensor, Clogged fuel injectors. 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
P0171 1999 Ford F150 indicates Fuel Injection System Too Lean Bank 1.
Common causes
Common causes include Vacuum leak, Faulty oxygen sensor, Clogged fuel injectors.
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.
What is this?
Table of contents Created and updated by William Orellana on Sep 10, 2024
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Code P0171 1999 Ford F150 Description

The P0171 code on a 1999 Ford F150 indicates that the fuel injection system on bank 1 is operating too lean. This means that there is an imbalance in the air-fuel mixture being delivered to the engine, with too much air or too little fuel present. This can lead to a variety of issues, including poor fuel economy, reduced engine performance, and potential damage to the engine over time.

OBDII Code P0171 1999 Ford F150 - Fuel Injection System Too Lean Bank 1
P0171 1999 Ford F150 Code - Fuel Injection System Too Lean Bank 1

Common Causes of P0171 1999 Ford F150

  1. Vacuum leak
  2. Faulty oxygen sensor
  3. Clogged fuel injectors
  4. Malfunctioning mass airflow sensor
  5. Fuel pump malfunction

Symptoms of P0171 1999 Ford F150

  1. Rough idle
  2. Engine misfires
  3. Loss of power during acceleration
  4. Poor fuel economy
  5. Stalling

How to Fix P0171 1999 Ford F150

  1. Perform a thorough inspection of the fuel injection system to identify the root cause of the lean condition.
  2. Repair or replace any faulty components, such as the oxygen sensor, mass airflow sensor, or fuel injectors.
  3. Check for vacuum leaks and repair as needed.
  4. Clear the diagnostic trouble codes from the engine control module and reset the fuel trims.
  5. Test drive the vehicle to ensure that the issue has been resolved and that the fuel mixture is now within the proper parameters.

Cost to Fix P0171 1999 Ford F150

The cost of repairing a P0171 code on a 1999 Ford F150 can vary depending on the specific cause of the lean condition and the extent of the repairs needed. On average, the cost of parts and labor for this issue can range from $200 to $500. However, it's important to note that diagnostic time and labor rates at auto repair shops can vary, so it's recommended to get a detailed estimate from a qualified mechanic before proceeding with the repairs.

What does this mean?

Tech Notes for P0171 1999 Ford F150

If the P0171 is combined with the P0174 code, it's very likely that the problem is caused by an intake leak. If there are no intake leaks, the next step is to replace the air filter and clean the air flow meter. If the problem persists the front oxygen (O2) sensor may need to be replaced.



The Adaptive Fuel Strategy continuously monitors fuel delivery hardware. The test fails when the adaptive fuel tables reach a rich calibrated limit.

When is the Code Detected?

- Fuel injection system does not operate properly.
- The amount of mixture ratio compensation is too small. (The mixture ratio is too lean.)

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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 P0171 1999 Ford F150 Code

1. What are common symptoms of OBDII code P0171 in a 1999 Ford F150?

The common symptoms of OBDII code P0171 in a 1999 Ford F150 include rough idle, lack of power, hesitation during acceleration, and an illuminated check engine light.

2. What are the possible causes of code P0171 in a 1999 Ford F150?

Common causes of OBDII code P0171 in a 1999 Ford F150 include a vacuum leak, faulty oxygen sensor, dirty or clogged fuel injectors, low fuel pressure, or a malfunctioning mass airflow sensor.

3. How can I diagnose the OBDII code P0171 in my 1999 Ford F150?

To diagnose OBDII code P0171 in a 1999 Ford F150, you can start by checking for vacuum leaks, inspecting the oxygen sensor, cleaning the fuel injectors, testing the fuel pressure, and examining the mass airflow sensor.

4. Can a dirty air filter trigger code P0171 in a 1999 Ford F150?

Yes, a dirty air filter can restrict airflow to the engine, causing a lean fuel mixture, which may trigger OBDII code P0171 in a 1999 Ford F150.

5. How do I repair OBDII code P0171 in my 1999 Ford F150?

To repair OBDII code P0171 in a 1999 Ford F150, you may need to fix any vacuum leaks, replace the oxygen sensor if faulty, clean or replace clogged fuel injectors, address low fuel pressure issues, or replace a malfunctioning mass airflow sensor.

6. Is it safe to continue driving my 1999 Ford F150 with OBDII code P0171?

It is not recommended to continue driving your 1999 Ford F150 with OBDII code P0171, as a lean fuel mixture can lead to engine damage over time. It's best to address the issue promptly.

7. Can a bad fuel pump cause OBDII code P0171 in a 1999 Ford F150?

Yes, a failing fuel pump can result in low fuel pressure, leading to a lean fuel mixture and triggering OBDII code P0171 in a 1999 Ford F150.

8. Will resetting the check engine light fix OBDII code P0171 in a 1999 Ford F150?

Resetting the check engine light may temporarily clear the code, but it will not fix the underlying issue causing OBDII code P0171 in a 1999 Ford F150. It's important to diagnose and repair the problem to prevent it from recurring.

9. Can a faulty EGR valve be responsible for OBDII code P0171 in a 1999 Ford F150?

Yes, a malfunctioning EGR (Exhaust Gas Recirculation) valve can disrupt the air-fuel mixture, potentially causing a lean condition and triggering OBDII code P0171 in a 1999 Ford F150.

10. How much does it typically cost to repair OBDII code P0171 in a 1999 Ford F150?

The cost to repair OBDII code P0171 in a 1999 Ford F150 can vary depending on the specific cause of the issue. Repairs may range from a simple fix like replacing a vacuum hose to more complex solutions like replacing a faulty oxygen sensor or fuel pump. It's best to consult with a mechanic for an accurate estimate.

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  • I have a 2000 ford f150 v6,and last night I notice a light sputter before I park. This morning I was driving and I started to turn off when I would stop. BUT in park it stays on. It drives as long as you give it gas.

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