how to fix P0300 code in Toyota Highlander XU70 (2020-Present)

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the battery to ensure safety while working on the engine.

Tools Required:

• OBD-II scanner
• Socket set
• Torque wrench
• Fuel pressure gauge
• Compression tester

2. Replace Spark Plugs

1. Remove the engine cover if applicable.
2. Disconnect the ignition coils from the spark plugs.
3. Use a spark plug socket to remove the old spark plugs.
4. Inspect the new spark plugs for correct gap (consult the owner’s manual for specifications).
5. Install new spark plugs by hand to avoid cross-threading, then tighten to the manufacturer's torque specifications.

3. Inspect and Replace Ignition Coils

1. Remove the ignition coils from each cylinder by unbolting them and gently pulling them out.
2. Inspect the coil connectors and terminals for corrosion or damage.
3. Install new ignition coils, ensuring they are seated properly on the spark plugs.
4. Reconnect the electrical connectors to the coils.

4. Check and Repair Fuel System

1. Connect the fuel pressure gauge to the fuel rail service port.
2. Turn the ignition to the "ON" position (do not start the engine) and check fuel pressure readings against manufacturer specifications.
3. If pressure is low, inspect the fuel filter and fuel pump for potential replacement.

5. Inspect for Vacuum Leaks

1. Visually inspect all vacuum lines for cracks or disconnections.
2. Use a smoke machine or carburetor cleaner to test for leaks around the intake manifold and vacuum connections.
3. Repair or replace any damaged lines or gaskets as necessary.

6. Perform a Compression Test

1. Remove the ignition coils and spark plugs to access cylinder chambers.
2. Insert the compression tester into the spark plug hole of each cylinder.
3. Crank the engine and note the compression readings for all cylinders; compare to manufacturer specifications.
4. Address any cylinders with low compression by exploring further for mechanical issues (e.g., valve problems, head gasket failure).