how to diagnose P0171 code in Toyota Corolla E210 (2019-2024)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to ensure safety during repairs.
• Allow the engine to cool down before working on components.

2. Inspect and Repair Air Intake System

• Sub-steps:
  1. Visually inspect the air intake ducting and hoses for cracks or disconnections.
  2. Tighten or replace any loose or damaged hoses.
  3. If applicable, replace the air filter.
• Tools Required: Screwdriver set, hose clamps, replacement hoses (if necessary).

3. Check and Clean MAF Sensor

• Sub-steps:
  1. Locate the MAF sensor in the air intake system.
  2. Disconnect the electrical connector and remove the sensor.
  3. Clean the MAF sensor with MAF cleaner spray; avoid touching the sensor element.
  4. Reinstall the MAF sensor and reconnect the electrical connector.
• Tools Required: MAF cleaner spray, screwdriver set.

4. Test Fuel Pressure

• Sub-steps:
  1. Connect a fuel pressure gauge to the fuel rail's test port.
  2. Turn the ignition to the "ON" position (do not start) and check the pressure reading.
  3. Compare the reading to the manufacturer's specifications (usually between 40-50 psi).
  4. If the pressure is low, inspect the fuel pump, fuel filter, and fuel lines for issues.
• Tools Required: Fuel pressure gauge.

5. Inspect and Test Oxygen Sensors

• Sub-steps:
  1. Locate the upstream and downstream oxygen sensors.
  2. Disconnect the electrical connectors from both sensors.
  3. Use a multimeter to check the resistance and ensure both sensors are functioning properly.
  4. Replace any faulty oxygen sensors.
• Tools Required: Multimeter, wrench set.

6. Verify Fuel Injector Function

• Sub-steps:
  1. Remove the fuel injector connectors.
  2. Test the resistance of each fuel injector with a multimeter; replace any that are out of spec.
  3. Perform a cleaning procedure if injectors are clogged.
• Tools Required: Multimeter, injector cleaning kit.