how to fix P0171 code in Honda Civic 10th Generation (2016-2021)

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool completely before beginning repairs.

2. Inspect and Repair Vacuum Leaks

• Sub-steps:

  1. Visually inspect all vacuum hoses connected to the intake manifold and air intake system for cracks or disconnections.
  2. Use a smoke machine or carb cleaner to detect leaks—spray around suspected areas and listen for changes in engine RPM.
  3. Replace any damaged hoses or gaskets as needed.

• Tools Required: Vacuum gauge, smoke machine, or carb cleaner.

3. Clean or Replace MAF Sensor

• Sub-steps:

  1. Locate the MAF sensor on the air intake duct.
  2. Disconnect the electrical connector and unscrew the sensor from the duct.
  3. Clean the sensor using MAF sensor cleaner and let it dry.
  4. If cleaning does not resolve the issue, replace the MAF sensor with a new unit.

• Tools Required: Screwdriver set, MAF sensor cleaner.

4. Check 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 the engine) and check the fuel pressure—ensure it meets manufacturer specifications.
  3. If the pressure is low, inspect the fuel pump and fuel filter for clogs or failures, and replace if necessary.

• Tools Required: Fuel pressure gauge.

5. Inspect 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; it should fluctuate between 0.1 to 0.9 volts.
  3. Replace the oxygen sensor if it is not operating within this range.

• Tools Required: Multimeter, oxygen sensor socket.