how to fix P0171 code in Toyota RAV4 Fourth Generation (2013-2018)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to prevent electrical short circuits.
• Allow the engine to cool before working on it.

2. Inspect and Repair Vacuum Leaks

• Sub-steps:
  • Visually inspect all vacuum lines and connections for cracks or disconnections.
  • Use a smoke machine or carburetor cleaner to identify leaks by spraying around suspected areas and observing RPM changes.
  • Replace any damaged vacuum hoses and reseal connections as needed.

3. Clean the Mass Air Flow (MAF) Sensor

• Tools Required: MAF sensor cleaner
• Sub-steps:
  • Locate the MAF sensor in the air intake duct.
  • Disconnect the electrical connector.
  • Remove the MAF sensor from the intake duct (typically requires a Torx or Phillips screwdriver).
  • Spray MAF sensor cleaner onto the sensor elements (do not touch).
  • Allow it to dry completely before reinstalling.
  • Reconnect the electrical connector.

4. Check and Correct Fuel System Pressure

• Tools Required: Fuel pressure gauge
• Sub-steps:
  • Locate the fuel rail and connect the fuel pressure gauge to the test port.
  • Turn the ignition key to the "On" position without starting the engine to check the pressure.
  • Compare the reading to the manufacturer's specifications (typically around 30-40 psi).
  • If the pressure is low, inspect the fuel pump and fuel filter for faults.

5. Inspect Fuel Injectors

• Sub-steps:
  • Visually inspect the fuel injectors for signs of leakage or damage.
  • Use a noid light to check if the injectors are receiving the proper signal from the ECM.
  • Replace any faulty injectors.

6. Verify Oxygen Sensor Function

• Sub-steps:
  • Use a multimeter to check the voltage output of the upstream oxygen sensor (should fluctuate between 0.1 to 0.9 volts).
  • Replace the oxygen sensor if it is outside the specified range or is not functioning.