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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the battery to ensure safety.
• Allow the engine to cool down before working.

2. Inspect and Repair Air Intake

• Remove the air intake duct connected to the throttle body.
• Visually inspect for cracks or loose connections. Tighten or replace any damaged components.
• Use a smoke machine or carburetor cleaner to detect vacuum leaks in the intake manifold and surrounding hoses.

3. Clean or Replace MAF Sensor

• Disconnect the electrical connector from the MAF sensor.
• Remove the sensor from the air intake duct.
• Clean the sensor with MAF cleaner spray (do not use other cleaners).
• If the sensor is damaged or cleaning does not resolve the issue, replace it with a new one.

4. Check and Repair Fuel System

• Connect a fuel pressure gauge to the fuel rail.
• Start the engine and observe the fuel pressure; it should be within the specified range (typically 30-50 psi).
• If pressure is low, check the fuel pump, filter, and fuel lines for blockages or failures. Replace as necessary.

5. Inspect Oxygen Sensors

• Locate the upstream (pre-catalytic converter) oxygen sensor.
• Disconnect the sensor's electrical connector and inspect the wiring for damage.
• Use a multimeter to check the sensor’s voltage output, ensuring it fluctuates between 0.1V and 0.9V when the engine is running.
• Replace the sensor if it fails the test.