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

Solution

1. Preparation

• Gather tools: OBD-II scanner, multimeter, fuel pressure gauge, socket set, torque wrench, and cleaning supplies.
• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the battery for safety.

2. Inspect and Repair Vacuum Leaks

• Check the intake manifold gaskets:
  • Remove the engine cover if necessary.
  • Use a visual inspection and a smoke machine if available to identify leaks.
  • Replace any damaged gaskets.
• Inspect vacuum hoses:
  • Check all hoses connected to the intake for cracks or disconnections.
  • Replace any damaged hoses.

3. Clean or Replace MAF Sensor

• Remove the MAF sensor:
  • Locate the MAF sensor in the intake air duct.
  • Disconnect the electrical connector and unbolt the sensor.
• Clean the MAF sensor:
  • Use MAF sensor cleaner spray to clean the sensor elements.
  • Allow it to dry before reinstalling.
• If damaged: Replace the MAF sensor with a new one.

4. Check and Adjust Fuel Pressure

• Connect the fuel pressure gauge:
  • Locate the fuel rail and connect the gauge to the test port.
• Start the engine and read the fuel pressure:
  • Ensure it meets the specifications (usually around 40-50 psi for most RAV4 engines).
• If low: Replace the fuel pump or filter as needed.

5. Inspect and Replace Oxygen Sensors

• Locate the O2 sensors:
  • There are typically two: upstream and downstream of the catalytic converter.
• Test the sensors with a multimeter:
  • Check for proper voltage output according to the manufacturer specifications (usually around 0.1 to 0.9 volts).
• Replace any faulty sensors.