how to fix P0174 lean code in Toyota Highlander XU70 (2020-Present)

Solution

1. Preparation

• Tools Required: OBD-II scanner, fuel pressure gauge, socket set, multimeter, cleaning solvent, vacuum gauge.
• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the battery to prevent any electrical shorts or shocks during repairs.

2. Inspect and Repair Air Intake System

1. Visual Inspection:
   • Check all hoses connected to the air intake for cracks or leaks.
   • Inspect the air filter; replace if dirty.
2. Seal Leaks:
   • Replace any damaged hoses or clamps.
   • Ensure the air intake duct is securely connected to the throttle body.

3. Clean or Replace MAF Sensor

1. Remove the MAF Sensor:
   • Locate the MAF sensor in the air intake duct.
   • Disconnect the electrical connector and unscrew the sensor from its housing.
2. Clean the Sensor:
   • Use MAF sensor cleaner to spray the sensor. Let it dry completely before reinstalling.
3. Reinstall the Sensor:
   • Secure the MAF sensor back into the duct and reconnect the electrical connector.

4. Check and Repair Fuel System

1. Fuel Pressure Test:
   • Connect the fuel pressure gauge to the fuel rail.
   • Turn the ignition to the "ON" position (without starting) to check pressure; refer to manufacturer specifications for correct values.
2. Replace Fuel Filter/Regulator:
   • If fuel pressure is low, replace the fuel filter or fuel pressure regulator as needed.
3. Test Fuel Injectors:
   • Use a multimeter to check the resistance of the fuel injectors; replace any that are out of specification.

5. Vacuum Leak Check

1. Inspect Vacuum Lines:
   • Look for any visible cracks or loose connections in the vacuum lines.
2. Use a Vacuum Gauge:
   • Connect a vacuum gauge to a manifold port and check for proper vacuum readings; replace any faulty vacuum lines.