how to fix P0174 code in Toyota Corolla E170 (2013-2019)

Learn how to diagnose and fix P0174 engine too lean condition in Toyota Corolla E170. Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to ensure safety while working on the vehicle.

2. Inspect and Repair Vacuum Leaks

• Tools Required: Vacuum gauge, smoke machine (optional)
• Inspect all vacuum hoses for cracks or disconnections.
• Use a vacuum gauge to test for leaks; replace any damaged hoses.
• If available, use a smoke machine to identify hard-to-find leaks in the intake manifold.

3. Check and Clean MAF Sensor

• Tools Required: MAF sensor cleaner
• Remove the MAF sensor from the air intake duct.
• Spray the MAF sensor with MAF cleaner and allow it to dry completely.
• Reinstall the MAF sensor and ensure it's properly connected.

4. Inspect and Test Fuel System

• Tools Required: Fuel pressure gauge
• Connect the fuel pressure gauge to the fuel rail and turn the ignition to the "ON" position (do not start the engine).
• Check the fuel pressure; it should be within the manufacturer's specified range (usually around 40-50 psi).
• If the pressure is low, check the fuel pump, fuel filter, and fuel lines for issues.

5. Inspect Oxygen Sensors

• Tools Required: O2 sensor socket
• Disconnect the electrical connector from the oxygen sensors.
• Remove the sensors using the O2 sensor socket and inspect for contamination.
• Replace any faulty sensors before reinstalling.

6. Clear Codes and Test Drive

• Reconnect the battery and use the OBD-II scanner to clear the P0174 code.
• Test drive the vehicle to ensure the check engine light does not reappear.