my Toyota RAV4 XA40 (2013-2018) has a check engine light with code P0171, what does it mean?

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shock.
• Allow the engine to cool down before starting work.

2. Inspect and Repair Vacuum Leaks

• Sub-steps:
  1. Visually inspect all vacuum hoses connected to the intake manifold for cracks or disconnections.
  2. Use a smoke machine or carburetor cleaner to locate any leaks. Spray around potential leak areas while the engine is running, and listen for changes in engine RPM.
  3. Replace any damaged hoses and ensure all connections are secure.

3. Clean or Replace MAF Sensor

• Tools Required: MAF sensor cleaner
• Sub-steps:
  1. Locate the MAF sensor in the air intake duct.
  2. Disconnect the electrical connector and remove the sensor from the duct.
  3. Spray the MAF sensor with MAF cleaner and gently clean the sensor wires.
  4. Allow it to dry completely before reinstalling the sensor.

4. Check Fuel System

• Sub-steps:
  1. Connect a fuel pressure gauge to the fuel rail to check the fuel pressure.
  2. If the pressure is below specifications, check the fuel pump and replace if necessary.
  3. Inspect and replace the fuel filter if it is clogged.

5. Inspect Oxygen Sensors

• Sub-steps:
  1. Locate the upstream (pre-catalytic converter) oxygen sensor.
  2. Disconnect the electrical connector and use a multimeter to test the sensor's voltage output; a healthy sensor should fluctuate between 0.1 to 0.9 volts.
  3. Replace the oxygen sensor if it fails the test.