what does it mean when my Toyota Highlander Fourth Generation (2020-present) has a P0301 code?

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, torque wrench, multimeter, compression tester, and basic hand tools.
• Safety Warnings: Disconnect the battery before working on electrical components.

2. Replace Spark Plug

• Remove the engine cover if applicable.
• Disconnect the ignition coil connector for cylinder 1.
• Remove the ignition coil bolts and take out the coil.
• Unscrew the spark plug using a spark plug socket.
• Inspect the spark plug for wear; if it is damaged or fouled, replace it with a new one.
• Reinstall the spark plug to the specified torque (typically around 13 lb-ft).
• Reinstall the ignition coil and reconnect the connector.

3. Test/Replace Ignition Coil

• If the ignition coil is faulty, replace it with a new one.
• Install the new ignition coil, ensuring it is securely fastened and connected.

4. Check/Fix Vacuum Leaks

• Inspect all vacuum hoses and connections for cracks or disconnections.
• Replace any damaged hoses.
• Use a smoke machine if necessary to detect hard-to-find leaks.

5. Inspect Fuel Injector

• Unplug the fuel injector connector for cylinder 1.
• Use a noid light to check for signal; if no signal, inspect wiring and connectors.
• If the injector is faulty, replace it with a new one and reconnect.

6. Compression Test

• Remove the spark plug from cylinder 1.
• Insert the compression tester into the spark plug hole.
• Crank the engine a few times and note the reading; it should be within the manufacturer's specifications (typically around 150-200 psi).
• If compression is low, further investigation into engine internals may be necessary.