what should I do if my Toyota Highlander Third Generation (2014-2019) has a P0300 code

Solution

1. Preparation

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

2. Inspect and Replace Spark Plugs

• Remove the ignition coil covers if applicable.
• Disconnect the electrical connectors from the ignition coils.
• Unscrew and remove the ignition coils using a socket set.
• Remove the old spark plugs using a spark plug socket and inspect for wear or damage.
• Install new spark plugs, ensuring they are gapped to manufacturer's specifications (typically around 0.043 inches for most Toyota engines).
• Reinstall the ignition coils and reconnect their electrical connectors.

3. Check and Replace Ignition Coils (if necessary)

• If any ignition coils were found defective during inspection, replace them.
• Ensure the new ignition coils are compatible with the specific engine model.
• Reinstall the ignition coils after replacement.

4. Inspect Fuel Injectors

• Use a fuel pressure gauge to check the fuel pressure at the rail.
• If pressure is low, inspect the fuel pump and filter for issues.
• Remove and clean fuel injectors if clogged, or replace them if faulty.

5. Inspect Vacuum Lines

• Visually inspect all vacuum lines for cracks or disconnections.
• Use a smoke machine or carburetor cleaner to check for leaks.
• Replace any damaged vacuum lines to restore proper operation.

6. Perform Compression Test

• Remove spark plugs for easier access to cylinders.
• Insert a compression gauge into each cylinder.
• Crank the engine and record the compression readings; compare them to the manufacturer's specifications.
• Address any cylinders with low compression by inspecting for valve or piston issues.