why does my Toyota RAV4 Fifth Generation (2019-present) have a check engine light with code P0171

Solution

1. Preparation

• Gather tools and parts needed for repair.
• Ensure the vehicle is parked on a level surface and the engine is off.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Repair Vacuum Leaks

• Sub-steps:
  1. Visually inspect vacuum lines and intake manifold for cracks or disconnections.
  2. Use a smoke machine or carburetor cleaner to identify leaks; apply around suspected areas and watch for changes in RPM.
  3. Replace any damaged hoses or gaskets.

3. Clean or Replace MAF Sensor

• Sub-steps:
  1. Locate the MAF sensor in the air intake duct.
  2. Disconnect the electrical connector and remove the sensor from the housing.
  3. Clean the MAF sensor with MAF cleaner spray, avoiding direct contact with the sensor element.
  4. If cleaning does not resolve the issue, replace the MAF sensor with a new one.

4. Check and Repair Fuel System

• Sub-steps:
  1. Connect a fuel pressure gauge to the fuel rail.
  2. Start the engine and observe the fuel pressure; compare it with manufacturer specifications.
  3. If the pressure is low, inspect and replace the fuel filter and fuel pump if necessary.

5. Inspect Engine Coolant Temperature (ECT) Sensor

• Sub-steps:
  1. Locate the ECT sensor on the engine.
  2. Using a multimeter, check the resistance of the ECT sensor at various temperatures.
  3. Replace the ECT sensor if readings are outside of specifications.