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Home/Cars/Toyota/Highlander/Third Generation (2014-2019)/how to fix P0171 code in Toyota Highlander Third Generation (2014-2019)

how to fix P0171 code in Toyota Highlander Third Generation (2014-2019)

Toyota Highlander Third Generation (2014-2019)

Severity: highDifficulty: mediumError Code: P01712-4 hours
4 min read
636 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 fuel system issue in Toyota Highlander (2014-2019). Step-by-step guide with diagnostic procedures and repair instructions.

Error Code
P0171
Component
Fuel System
Repair Time
2-4 hours

Safety Warnings

  • ⚠Disconnect battery before working on electrical systems.
  • ⚠Allow engine to cool before servicing intake or exhaust components.

Symptoms

  • •Check engine light illuminated
  • •Rough idle or stalling
  • •Loss of power during acceleration
  • •Poor fuel economy
  • •Increased emissions
  • •Engine backfiring or hesitation

Diagnostic Steps

  1. 1Scan the vehicle using an OBD-II scanner to confirm the P0171 code and check for any additional codes.
  2. 2Inspect the air intake system for any vacuum leaks or damaged hoses.
  3. 3Check the fuel system pressure using a fuel pressure gauge to ensure it meets manufacturer specifications.
  4. 4Examine the Mass Air Flow (MAF) sensor for dirt or contamination and test its functionality.
  5. 5Inspect the fuel injectors for proper operation and any leaks.
  6. 6Check the engine coolant temperature sensor for proper readings and functionality.
  7. 7Review the exhaust system for any leaks that may affect the air-fuel mixture.

Solution

Solution

1. Preparation

  • Gather required tools and parts.
  • Disconnect the negative battery terminal to prevent electrical shorts.
  • Allow the engine to cool before proceeding with repairs.

2. Inspect and Repair Air Intake System

  • Sub-steps:
    1. Remove the air filter housing and inspect the air filter. Replace if clogged.
    2. Visually inspect all intake hoses for cracks or disconnections, and replace as necessary.
    3. Check the throttle body for carbon buildup and clean if needed using throttle body cleaner.

3. Clean or Replace MAF Sensor

  • Sub-steps:
    1. Disconnect the electrical connector from the MAF sensor.
    2. Remove the MAF sensor from the intake duct.
    3. Clean the sensor using MAF cleaner and let it dry completely before reinstallation.
    4. Reinstall the sensor and reconnect the electrical connector.

4. Check and Repair Fuel System

  • Sub-steps:
    1. Using a fuel pressure gauge, connect it to the fuel rail and turn the ignition on (do not start the engine) to check for fuel pressure.
    2. If pressure is low, inspect the fuel pump, fuel filter, and fuel lines for blockages or damage.
    3. Test the fuel injectors using a multimeter to ensure they are receiving the correct voltage and are functioning properly.

5. Verify Coolant Temperature Sensor

  • Sub-steps:
    1. Locate the engine coolant temperature sensor and inspect its wiring for damage.
    2. Use a multimeter to check the sensor's resistance and compare it to manufacturer specifications.
    3. Replace the sensor if it is outside of specifications.

6. Exhaust System Inspection

  • Sub-steps:
    1. Inspect the exhaust system for any visible leaks or damage.
    2. Check the exhaust manifold and gaskets for integrity.
    3. Repair or replace any damaged components as necessary.

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
  • Fuel pressure gauge
  • Throttle body cleaner
  • Multimeter
  • Socket set
  • Screwdrivers

Parts Required

  • New air filter (if needed)
  • MAF sensor cleaner
  • Fuel filter (if needed)
  • Engine coolant temperature sensor (if needed)
  • Any damaged hoses or vacuum lines

Additional Information

Error CodeP0171
Component

Fuel System

Repair Time

2-4 hours

Difficulty

medium

Severity

high

Tools

6 items

Parts

5 items

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