how to fix P0171 code on my Toyota Corolla E210 (2019-2024)

Solution

1. Preparation

• Tools Required: OBD-II scanner, fuel pressure gauge, multimeter, basic hand tools, MAF cleaner, vacuum gauge.
• Disconnect the negative battery terminal to ensure safety during the repair process.

2. Inspect Air Intake System

• Remove the engine cover if applicable.
• Visually inspect all hoses connected to the air intake for cracks or disconnections.
• Use a vacuum gauge to check for leaks in the intake manifold by connecting it to the manifold vacuum port.
• If leaks are found, replace damaged hoses or gaskets.

3. Check Fuel Pressure

• Tools Required: Fuel pressure gauge.
• Locate the fuel pressure test port on the fuel rail.
• Connect the fuel pressure gauge to the port and turn the ignition to the "ON" position without starting the engine to check the pressure.
• Compare the reading with the manufacturer's specifications. If the pressure is low, inspect the fuel pump and filter.

4. Clean or Replace MAF Sensor

• Disconnect the MAF sensor electrical connector.
• Remove the MAF sensor from the air intake tube.
• Spray MAF cleaner on the sensor elements and let it dry completely.
• Reinstall the MAF sensor, ensuring a secure fit, and reconnect the electrical connector.

5. Inspect Oxygen Sensors

• Tools Required: Multimeter.
• Locate the upstream oxygen sensor (pre-catalytic converter).
• Use a multimeter to test the sensor's voltage output while the engine is running.
• If the readings are outside the normal range (typically 0.1 to 0.9 volts), replace the oxygen sensor.

6. Check Engine Coolant Temperature Sensor

• Locate the coolant temperature sensor.
• Use a multimeter to ensure the sensor resistance matches the specifications for current engine temperature.
• If it’s out of specification, replace the sensor.