how to fix the check engine light on my Toyota RAV4 XA40 (2013-2018) with code P0171

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool if it has been running.

2. Inspect and Repair Air Intake System

• Inspect for Vacuum Leaks:
  • Visually inspect all hoses and connections for cracks or disconnections.
  • Use a smoke machine or carburetor cleaner to check for leaks while the engine is running.
• Replace Damaged Hoses:
  • If any hoses are damaged, remove the faulty hoses using pliers.
  • Install new hoses, ensuring a secure fit and proper routing.

3. Clean or Replace MAF Sensor

• Remove MAF Sensor:
  • Locate the MAF sensor in the air intake duct.
  • Disconnect the electrical connector and remove the mounting screws with a Torx screwdriver.
• Clean MAF Sensor:
  • Use MAF sensor cleaner and a lint-free cloth to gently clean the sensor elements.
• Reinstall MAF Sensor:
  • Reinstall the sensor, ensuring it is securely mounted and the connector is reattached.

4. Check Fuel Pressure

• Connect Fuel Pressure Gauge:
  • Locate the fuel rail service port and connect the fuel pressure gauge.
• Test Pressure:
  • Turn the ignition to the "ON" position (do not start) and observe the pressure reading.
  • Compare the reading against manufacturer specifications (typically around 50-60 psi).
• Replace Fuel Pump if Necessary:
  • If pressure is low, relieve fuel system pressure, disconnect battery, and remove the fuel pump assembly to replace it.

5. Inspect and Replace Oxygen Sensor (if needed)

• Locate and Remove Oxygen Sensor:
  • Identify the upstream oxygen sensor in the exhaust manifold.
  • Use an oxygen sensor socket to remove the sensor.
• Install New Oxygen Sensor:
  • Apply anti-seize compound to the threads of the new sensor.
  • Install the new sensor and connect the electrical connector.

6. Clear Codes and Test Drive

• Clear DTCs:
  • Reconnect the negative battery terminal and use the OBD-II scanner to clear the trouble codes.
• Test Drive:
  • Drive the vehicle for a short distance (10-15 miles) to monitor for any reoccurrence of the check engine light.