how to diagnose P0301 code in Toyota Highlander XU70 (2020-Present)

Solution

1. Preparation

• Gather necessary tools and parts.
• Park the vehicle on a level surface and engage the parking brake.
• Disconnect the negative battery terminal to ensure safety.

2. Inspect and Replace Ignition Components

• Tools Required: Socket set, torque wrench, dielectric grease.
• Remove the engine cover if necessary.
• Disconnect the ignition coil connector and the bolt securing the ignition coil.
• Remove the ignition coil from cylinder 1 and inspect it for cracks or damage.
• Replace the spark plug in cylinder 1 if it shows signs of wear or damage. Ensure the gap is set to manufacturer's specifications.
• Apply dielectric grease to the ignition coil connector and reinstall it.

3. Check and Replace Fuel Injector

• Tools Required: Fuel injector puller, cleaning solvent.
• Disconnect the fuel injector connector and remove the retaining clip.
• Carefully pull the fuel injector from its bore. Inspect for carbon buildup or damage.
• Clean the injector with a suitable solvent or replace it if necessary.
• Reinstall the fuel injector and reconnect the connector.

4. Vacuum Leak Inspection and Repair

• Tools Required: Smoke machine (optional) or carburetor cleaner.
• Visually inspect all vacuum hoses connected to the intake manifold for cracks or disconnections.
• If accessible, use a smoke machine to identify any leaks; alternatively, spray carburetor cleaner around suspected areas while the engine is running to check for changes in idle speed.
• Repair or replace any damaged hoses or components.

5. Compression Test (if necessary)

• Tools Required: Compression tester.
• Remove the spark plug from cylinder 1.
• Insert the compression tester into the spark plug hole and crank the engine several times.
• Record the compression reading; it should be within the manufacturer's specified range. If it is low, further investigation into mechanical issues may be needed.