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

Solution

1. Preparation

• Tools Required: OBD-II scanner, basic socket set, fuel pressure gauge, MAF sensor cleaner, multimeter.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Repair Air Intake System

• Sub-steps:
  1. Visually inspect all air intake hoses and connections from the air filter to the throttle body.
  2. Tighten any loose connections and replace any damaged hoses.
  3. Check the air filter and replace it if it is dirty or clogged.

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 duct.
  3. Clean the MAF sensor using MAF sensor cleaner; do not touch the sensing elements.
  4. Reinstall the MAF sensor and reconnect the electrical connector.

4. Check and Repair Fuel System

• Sub-steps:
  1. Connect the fuel pressure gauge to the fuel rail and turn the ignition on without starting the engine.
  2. Verify that the fuel pressure is within the specified range (typically 43-50 PSI for most models).
  3. If pressure is low, inspect the fuel pump and replace it if necessary.
  4. Check the fuel injectors for proper operation; replace any faulty injectors.

5. Check Engine Coolant Temperature Sensor

• Sub-steps:
  1. Locate the coolant temperature sensor and disconnect the electrical connector.
  2. Use a multimeter to measure the resistance of the sensor; refer to the service manual for specification values.
  3. Replace the sensor if it is out of specification.