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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool down before starting work.

2. Inspect and Repair Intake System

• Step 1: Visually inspect all vacuum hoses for cracks or loose connections.
• Step 2: Use a smoke machine or carburetor cleaner to check for vacuum leaks.
• Step 3: If a leak is found, replace or reattach the affected hose or component.

3. Clean or Replace MAF Sensor

• Step 1: Remove the MAF sensor from the air intake duct using a Torx screwdriver.
• Step 2: Clean the MAF sensor with MAF sensor cleaner; do not use other types of cleaners.
• Step 3: Allow the sensor to dry completely before reinstalling it.

4. Test and Adjust Fuel System

• Step 1: Connect a fuel pressure gauge to the fuel rail.
• Step 2: Turn the ignition to the "ON" position to check fuel pressure; it should be within manufacturer specifications (usually around 43-50 PSI).
• Step 3: If the pressure is low, inspect the fuel pump, fuel filter, and regulator. Replace any faulty components.

5. Inspect and Service Oxygen Sensors

• Step 1: Locate the upstream and downstream oxygen sensors.
• Step 2: Use a socket wrench to remove the oxygen sensors.
• Step 3: Inspect the sensors for damage or excessive carbon buildup; clean or replace as necessary.