why does my Honda Accord fail emissions testing with P0171 code

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical issues while working.

2. Inspect and Repair Air Intake System

• Sub-steps:
  1. Visually inspect all vacuum hoses and connections for cracks or disconnections.
  2. Replace any damaged hoses or connections.
  3. Use a smoke machine if necessary to identify hard-to-find leaks.

3. Clean the Mass Air Flow (MAF) Sensor

• Sub-steps:
  1. Remove the MAF sensor from the air intake duct using a Torx or Phillips screwdriver.
  2. Use MAF cleaner spray to clean the sensor element. Do not touch it with fingers or any tools.
  3. Allow the sensor to dry completely before reinstallation.

4. Check Fuel Pressure

• Sub-steps:
  1. Locate the fuel pressure test port on the fuel rail.
  2. Connect a fuel pressure gauge to the test port.
  3. Turn the ignition key to the "ON" position (do not start the engine) and check the reading against the manufacturer's specifications.
  4. If pressure is low, investigate the fuel pump and filter for issues.

5. Examine Oxygen Sensors

• Sub-steps:
  1. Locate the upstream (pre-catalytic converter) oxygen sensor.
  2. Use a multimeter to check the sensor's voltage output while the engine is running.
  3. If the output is not within specified ranges, replace the sensor.

6. Test Fuel Injectors

• Sub-steps:
  1. Disconnect the fuel injector connectors.
  2. Use a multimeter to check the resistance of each injector to ensure they are within specifications.
  3. Replace any faulty fuel injectors.