how to fix P0171 code in Toyota Corolla E170 (2013-2019)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to ensure safety while working on electrical components.

2. Inspect and Repair Vacuum Leaks

• Sub-steps:
  1. Visually inspect all vacuum lines for cracks or disconnections.
  2. Use a smoke machine or carburetor cleaner to identify leaks by spraying around suspected areas and watching for changes in idle.
  3. Replace any damaged vacuum hoses or gaskets immediately.

3. Clean or Replace MAF Sensor

• Tools Required: MAF sensor cleaner, screwdriver
• Sub-steps:
  1. Locate the MAF sensor in the air intake duct.
  2. Disconnect the electrical connector and unscrew the sensor from the duct.
  3. Clean the sensor using MAF cleaner; do not touch the sensor element.
  4. Reinstall the sensor and reconnect the electrical connector.

4. Test and Repair Fuel System

• Tools Required: Fuel pressure gauge
• Sub-steps:
  1. Connect the fuel pressure gauge to the fuel rail's test port.
  2. Turn the ignition to the "ON" position without starting the engine and check the fuel pressure.
  3. If pressure is below specifications (usually around 43-50 psi), inspect the fuel pump and filter.
  4. Replace the fuel filter if clogged and test the fuel pump for proper operation.

5. Check and Replace ECT Sensor (if needed)

• Sub-steps:
  1. Locate the engine coolant temperature sensor.
  2. Disconnect the electrical connector and remove the sensor.
  3. Test the sensor using a multimeter for proper resistance values according to specifications.
  4. Replace the sensor if it is out of range.

6. Clear Codes and Test Drive

• After completing repairs, use the OBD-II scanner to clear the P0171 code.
• Test drive the vehicle to ensure the check engine light does not reappear and that the engine runs smoothly.