how to fix P0174 system too lean in Toyota Highlander Third Generation (2014-2019)

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the negative battery terminal to ensure safety.
• Allow the engine to cool completely before starting work.

2. Inspect and Repair Air Intake System

• Tools Required: Basic socket set, torque wrench, vacuum gauge
• Check all vacuum hoses connected to the intake manifold for cracks or disconnections.
• Use a vacuum gauge to test for vacuum leaks; replace any faulty hoses.
• Inspect the intake manifold gasket for signs of wear or damage; replace if necessary.

3. Clean or Replace MAF Sensor

• Tools Required: MAF sensor cleaner
• Disconnect the electrical connector from the MAF sensor.
• Remove the MAF sensor from the intake system.
• Clean the sensor using MAF sensor cleaner to remove dirt and debris.
• Reinstall the MAF sensor and reconnect the electrical connector.

4. Check Fuel Pressure and Injectors

• Tools Required: Fuel pressure gauge, noid light
• Connect the fuel pressure gauge to the fuel rail and turn the ignition on (do not start the engine) to check fuel pressure.
• Compare the reading with the manufacturer's specifications; if low, check the fuel pump and filter.
• If fuel pressure is adequate, use a noid light to check the injector pulse when the engine is cranked; replace any faulty injectors.

5. Clean Throttle Body

• Tools Required: Throttle body cleaner, soft cloth
• Remove the throttle body from the intake manifold.
• Spray throttle body cleaner on the throttle plate and inside the throttle body.
• Wipe clean with a soft cloth to remove carbon buildup; ensure the throttle plate operates smoothly.
• Reinstall the throttle body and reconnect all hoses and electrical connectors.