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

Solution

1. Preparation

• Gather tools and parts. Disconnect the negative battery terminal to prevent any electrical shorts.
• Tools Required: OBD-II scanner, multimeter, socket set, torque wrench, fuel pressure gauge, cleaning supplies.

2. Inspect and Repair Vacuum Leaks

• Visually inspect all vacuum hoses connected to the intake manifold for cracks or disconnections.
• Use a smoke machine or carburetor cleaner to find leaks by spraying around hose connections and intake gaskets while the engine is running. Look for RPM changes indicating a leak.
• Replace any damaged hoses and reseal gaskets as needed.

3. Clean or Replace MAF Sensor

• Locate the MAF sensor in the air intake duct.
• Remove the sensor using a socket set (usually Torx screws).
• Clean the sensor with MAF cleaner spray. Do not touch the sensing element.
• If cleaning does not resolve issues, replace the MAF sensor with a new one.

4. Check and Adjust Fuel Pressure

• Connect a fuel pressure gauge to the fuel rail test port.
• Turn the ignition to the "ON" position (do not start) and observe the pressure reading. Compare it to manufacturer specifications (usually around 40-50 psi).
• If the pressure is low, inspect the fuel filter and fuel pump for blockages or failures. Replace as necessary.

5. Inspect Fuel Injectors

• Remove the fuel rail to access the injectors.
• Visually inspect for cracks or leaks around the injectors.
• Clean the injectors using a dedicated fuel injector cleaning kit or replace them if necessary.

6. Reassemble and Clear Codes

• Reinstall all components in reverse order of removal.
• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0171 code and check for any new codes after repairs.