how to fix P0171 and P0174 codes on my Ford F-150 13th Generation (2015-2020)

Ford F-150 13th Generation (2015-2020)

Error Codes

2-4 hours

Time

medium

Difficulty

high

Severity

Error Code: P0171, P0174

4 min read

648 words

⚠️ Safety Warning

This issue requires immediate attention. If you are not experienced with automotive repairs, consult a professional mechanic. Working on critical systems can be dangerous.

Problem Statement

Learn how to diagnose and fix P0171 and P0174 codes in your Ford F-150. Step-by-step guide with symptoms, diagnostic steps, and repair instructions.

Error Code

P0171, P0174

Affected Component

Engine

Estimated Time

2-4 hours

⚠️ Safety Warnings

Important safety information - read before proceeding

•Disconnect the battery before working on electrical systems.
•Allow the engine to cool before opening any components.

Symptoms

•Check engine light illuminated
•Rough idle at startup
•Decreased fuel efficiency
•Engine stalling or hesitation during acceleration
•Increased engine noise or backfiring

Diagnostic Steps

1
Scan the vehicle's computer using an OBD-II scanner to confirm the presence of the P0171 and P0174 codes.
2
Inspect the intake system for vacuum leaks, including hoses, gaskets, and the intake manifold.
3
Check the fuel pressure using a fuel pressure gauge to ensure it meets manufacturer specifications.
4
Examine the mass air flow (MAF) sensor for proper operation and cleanliness.
5
Inspect the fuel injectors for clogs or failure.
6
Test the oxygen sensors for correct functionality and response times.

Solution

💡 Expert Tip

For complex repairs like this, consider taking photos at each step. This helps if you need to reverse a step or consult with a mechanic. Also, keep all removed parts organized - you may need to reference them during reassembly.

Verification

After completing the repair, verify that the issue has been resolved:

✓Test the affected component to ensure it functions correctly
✓Check for any error codes or warning lights
✓Monitor the vehicle for a few days to ensure the issue does not recur

Prevention Tips

To prevent this issue from occurring again:

•Follow the manufacturer's recommended maintenance schedule
•Address warning signs early before they develop into major issues
•Use quality parts and fluids recommended for your vehicle
•Keep detailed records of all repairs and maintenance

Tools & Equipment Required

•OBD-II scanner
•Vacuum gauge
•Fuel pressure gauge
•MAF sensor cleaner
•Multimeter
•Fuel line disconnect tool
•Socket set
•O2 sensor socket

Parts Required

•Vacuum hoses (if needed)
•MAF sensor (if faulty)
•Fuel filter (if clogged)
•Fuel injectors (if defective)
•Oxygen sensors (if testing indicates failure)

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Diagnostic Steps

1
Scan the vehicle's computer using an OBD-II scanner to confirm the presence of the P0171 and P0174 codes.
2
Inspect the intake system for vacuum leaks, including hoses, gaskets, and the intake manifold.
3
Check the fuel pressure using a fuel pressure gauge to ensure it meets manufacturer specifications.
4
Examine the mass air flow (MAF) sensor for proper operation and cleanliness.
5
Inspect the fuel injectors for clogs or failure.
6
Test the oxygen sensors for correct functionality and response times.

Solution

1. Preparation

Gather all necessary tools and parts.
Ensure the vehicle is parked on a flat surface and the engine is cool.
Disconnect the battery to prevent any electrical shorts.

2. Inspect and Repair Vacuum Leaks

Tools Required: Vacuum gauge, hose clamps, screwdriver set.
Inspect all vacuum hoses for cracks or disconnections. Replace any damaged hoses.
Check intake manifold gaskets for leaks. Replace if necessary.
Use a vacuum gauge to identify leaks; a steady vacuum reading indicates no leaks.

3. Clean or Replace MAF Sensor

Tools Required: MAF sensor cleaner, Torx or socket wrench set.
Disconnect the MAF sensor electrical connector and remove the sensor from the air intake.
Spray MAF sensor cleaner onto the sensor components. Allow it to dry completely before reinstallation.
Reattach the MAF sensor and electrical connector.

4. Check and Adjust Fuel Pressure

Tools Required: Fuel pressure gauge, fuel line disconnect tool.
Attach the fuel pressure gauge to the fuel rail. Turn the ignition to the ON position without starting the engine to check pressure.
Ensure the fuel pressure matches the manufacturer's specifications (typically 30-50 psi for most F-150 models).
If pressure is low, inspect the fuel pump and fuel filter for issues.

5. Inspect Fuel Injectors

Tools Required: Multimeter, fuel injector cleaner.
Test each injector for proper resistance using a multimeter (typically 12-16 ohms).
If any injector is out of specification, replace it.
Use a fuel injector cleaner if injectors are clogged.

6. Test and Replace Oxygen Sensors (if necessary)

Tools Required: O2 sensor socket, multimeter.
Disconnect the oxygen sensor connectors and check their voltage output with a multimeter.
If readings are outside the specified range or if response times are slow, replace the oxygen sensors.