what does it mean if my Toyota Highlander has a check engine light and a P0301 code

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shock.
• Ensure the vehicle is parked on a level surface and the engine is cool.

2. Inspect and Replace Spark Plug

• Step 1: Remove the engine cover (if applicable) to access the ignition components.
• Step 2: Remove the spark plug wire or ignition coil from cylinder 1.
• Step 3: Use a spark plug socket and ratchet to remove the spark plug.
• Step 4: Inspect the spark plug for wear or fouling. If damaged, replace with a new spark plug (specifications: NGK or Denso, gap as per manufacturer).
• Step 5: Reinstall the spark plug and reconnect the ignition coil or spark plug wire.

3. Inspect and Replace Ignition Coil (if necessary)

• Step 1: If the spark plug appears normal, proceed to inspect the ignition coil for cylinder 1.
• Step 2: Remove the ignition coil from cylinder 1 by unscrewing the mounting bolts.
• Step 3: Inspect the ignition coil for cracks or damage. Replace with a new coil if defective.
• Step 4: Reinstall the ignition coil and secure it with bolts.

4. Check and Clean Fuel Injector

• Step 1: Disconnect the fuel injector connector for cylinder 1.
• Step 2: Use a noid light to check for proper electrical signal to the fuel injector.
• Step 3: If the injector is not firing, replace it with a new fuel injector.
• Step 4: If the injector is firing, clean it with a fuel injector cleaner and reinstall.

5. Compression Test (if misfire persists)

• Step 1: Remove all spark plugs for easier access to the cylinders.
• Step 2: Insert a compression gauge into the spark plug hole of cylinder 1.
• Step 3: Crank the engine and record the compression reading. Compare with specifications (typically 170-200 psi).
• Step 4: If compression is low, further diagnostics may be needed for internal engine issues.