what does it mean if my Toyota Corolla E170 (2013-2019) shows code P0171?

Solution

1. Preparation

• Gather necessary tools and parts.
• Park the vehicle on a level surface and engage the parking brake.
• Disconnect the negative battery cable to prevent electrical shorts.

2. Inspect for Vacuum Leaks

• Use a smoke machine or spray soapy water around intake hoses and gaskets.
• Listen for hissing sounds indicating leaks.
• Replace any damaged hoses or gaskets as necessary.

3. Clean or Replace the MAF Sensor

• Locate the MAF sensor in the air intake duct.
• Disconnect the electrical connector and remove the sensor.
• Clean the sensor with MAF cleaner or replace it if damaged.
• Reinstall the sensor and reconnect the electrical connector.

4. Check Fuel Pressure

• Connect a fuel pressure gauge to the fuel rail's service port.
• Turn the ignition key to the "ON" position (do not start) and note the pressure reading.
• Compare the reading to the manufacturer's specifications (usually between 40-50 psi).
• If pressure is low, consider replacing the fuel pump or filter.

5. Inspect Throttle Body

• Remove the air intake duct to access the throttle body.
• Use a throttle body cleaner and a soft cloth to clean the throttle body.
• Ensure the throttle plate operates smoothly without binding.

6. Test and Replace Oxygen Sensors (if needed)

• Use a multimeter to check the voltage output of the upstream oxygen sensor.
• If the reading is outside the normal range (0.1 to 0.9 volts), replace the sensor.
• Reconnect the sensor, ensuring a secure fit.