my Honda Civic 9th Generation (2012-2015) has a check engine light and code P0171

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the negative battery terminal to avoid electrical issues.
• Allow the engine to cool down before starting work.

2. Inspect and Repair Vacuum Leaks

• Tools Required: Vacuum gauge, flashlight
• Inspect all vacuum hoses for cracks or disconnections.
• Use a vacuum gauge to check for proper readings; a reading lower than normal indicates a leak.
• Replace any damaged hoses and reattach any loose connections.

3. Clean or Replace MAF Sensor

• Tools Required: MAF cleaner, screwdriver
• Carefully remove the MAF sensor from the air intake.
• Spray MAF sensor cleaner on the sensing elements; do not touch them.
• Allow the sensor to dry completely before reinstalling.
• If the sensor is damaged, replace it with a new one.

4. Check Fuel Pressure

• Tools Required: Fuel pressure gauge
• Locate the fuel rail service port and attach the fuel pressure gauge.
• Turn the ignition to the "ON" position (do not start the engine) and check the pressure reading; it should be within the manufacturer's specifications (usually around 40-50 psi).
• If pressure is low, check the fuel pump and fuel filter for issues and replace if necessary.

5. Inspect Oxygen Sensors

• Tools Required: O2 sensor socket, multimeter
• Locate the upstream oxygen sensor and unplug the electrical connector.
• Use a multimeter to check for proper voltage output; it should fluctuate between 0.1 to 0.9 volts.
• If the sensor is malfunctioning, replace it with a new one.

6. Reassemble and Test

• Reconnect all components and hoses removed during the repair.
• Reconnect the negative battery terminal.
• Start the engine and observe for any abnormal sounds or warning lights.