why does my Toyota Camry XV70 (2018-2024) have a check engine light with code P0171

Solution

1. Preparation

• Gather tools: OBD-II scanner, fuel pressure gauge, multimeter, socket set, cleaning supplies, and safety glasses.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Repair Air Intake System

• Sub-step 1: Visually inspect vacuum hoses for cracks or disconnections. Replace any damaged hoses.
• Sub-step 2: Check the intake manifold gasket for leaks. If leaking, replace the gasket using a torque wrench to tighten bolts to the manufacturer's specifications (typically around 15-22 ft-lbs).
• Sub-step 3: Clean the throttle body and ensure the throttle plate moves freely.

3. Test and Repair Fuel System

• Sub-step 1: Connect the fuel pressure gauge to the fuel rail and turn the ignition to the "ON" position (do not start). The pressure should typically be around 40-50 psi for a Camry. If low, check the fuel pump operation and replace it if necessary.
• Sub-step 2: Inspect and clean the fuel injectors using a fuel injector cleaner or replace them if malfunctioning.

4. Clean or Replace MAF Sensor

• Sub-step 1: If the MAF sensor is dirty, use MAF sensor cleaner to clean it gently. Allow it to dry completely before reconnecting.
• Sub-step 2: If damaged, replace the MAF sensor and ensure proper connection.

5. Check Coolant Temperature Sensor

• Sub-step 1: Using a multimeter, test the coolant temperature sensor for proper resistance values according to the service manual specifications.
• Sub-step 2: Replace the sensor if it does not meet specifications.