how to fix P0300 code in my Toyota Highlander Third Generation (2014-2019)

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, torque wrench, fuel pressure gauge, multimeter, compression tester.
• Ensure the vehicle is parked on a level surface and the engine is turned off.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Spark Plugs

• Remove the engine cover if necessary.
• Using a socket set, carefully remove the spark plug wires or ignition coils (depending on your engine type).
• Inspect the spark plugs for wear and carbon buildup.
• If any plugs are worn or damaged, replace them with OEM or equivalent plugs, ensuring the gap is set to manufacturer specifications.
• Reinstall the ignition coils or spark plug wires.

3. Check and Replace Ignition Coils

• If the spark plugs are fine, check the ignition coils using a multimeter to ensure they are functioning correctly (consult the service manual for resistance specifications).
• Replace any faulty ignition coils with new, OEM coils.
• Reinstall all components removed for access.

4. Fuel System Inspection

• Connect a fuel pressure gauge to the fuel rail to check for proper fuel pressure (consult manufacturer specifications).
• If the pressure is low, inspect or replace the fuel filter and fuel pump as needed.

5. Air Intake and Vacuum Inspection

• Inspect the air intake duct for any obstructions or damage, ensuring the MAF sensor is clean and functioning.
• Check all vacuum hoses for cracks or disconnections and replace any damaged hoses.

6. Compression Test

• If misfire symptoms persist, perform a compression test on all cylinders.
• If any cylinder has low compression, further diagnosis may be necessary to check for valve or head gasket issues.