how to fix P0171 code in Honda Civic 9th Generation (2012-2015)

Solution

1. Preparation

• Gather tools and parts. Ensure the vehicle is on a flat surface and the engine is cool.
• Disconnect the negative battery terminal to avoid electrical shorts.

2. Inspect and Repair Vacuum Leaks

• Sub-steps:
  1. Visually inspect all vacuum hoses connected to the intake manifold for cracks or disconnections.
  2. Use a smoke machine or carb cleaner to identify leaks. Apply around suspected areas while monitoring RPM changes.
  3. Replace any damaged hoses with OEM replacements.

Tools Required:

• Smoke machine or carb cleaner
• Pliers
• Replacement vacuum hoses

3. Clean or Replace MAF Sensor

• Sub-steps:
  1. Locate the MAF sensor on the air intake tube.
  2. Disconnect the electrical connector and remove the sensor.
  3. Clean the MAF sensor using MAF cleaner spray. Avoid touching the sensor elements.
  4. If the sensor is faulty, replace it with a new one.

Tools Required:

• MAF sensor cleaner
• Screwdriver set

4. Test and Repair Fuel System

• Sub-steps:
  1. Connect a fuel pressure gauge to the fuel rail test port.
  2. Turn the ignition key to the "ON" position (do not start the engine) and check the fuel pressure; it should match specifications (typically 40-50 psi).
  3. If pressure is low, check the fuel pump relay and fuse. Replace the fuel pump if necessary.
  4. Replace the fuel filter if it hasn't been changed recently.

Tools Required:

• Fuel pressure gauge
• Screwdriver set
• Wrench set

5. Inspect and Test Oxygen Sensors

• Sub-steps:
  1. Locate the upstream oxygen sensor (pre-catalytic converter).
  2. Use a multimeter to check the sensor's voltage output while the engine is running (should oscillate between 0.1-0.9 volts).
  3. If the sensor is not functioning correctly, replace it with a new one.

Tools Required:

• Multimeter
• Oxygen sensor socket

6. Check Fuel Injectors

• Sub-steps:
  1. Remove the fuel rail to access the injectors.
  2. Inspect injectors for clogs or leaks. Replace any faulty injectors.
  3. Clean the injectors using an ultrasonic cleaner if necessary.

Tools Required:

• Injector cleaner kit
• Wrench set