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

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool down before starting work.

2. Replace Spark Plugs

• Sub-steps:
  1. Remove the engine cover (if applicable) by unscrewing the retaining bolts.
  2. Using a spark plug socket, remove each spark plug and inspect them for wear or carbon buildup.
  3. Gap new spark plugs according to manufacturer specifications (typically 0.044 inches for Toyota).
  4. Install new spark plugs by hand to avoid cross-threading, then torque to specification (usually around 13 lb-ft).

3. Inspect and Replace Ignition Coils

• Sub-steps:
  1. Disconnect the wiring harness from each ignition coil.
  2. Remove each ignition coil by unbolting it from the engine.
  3. Test each coil with a multimeter; replace any that are outside the specified resistance range.
  4. Install new ignition coils, ensuring the connectors are secure.

4. Clean or Replace Fuel Injectors

• Sub-steps:
  1. Remove the fuel rail by detaching the bolts and carefully lifting it off the injectors.
  2. Inspect the injectors for clogs; clean using a professional fuel injector cleaning kit or replace if necessary.
  3. Reinstall the fuel rail and ensure all connections are tight.

5. Check for Vacuum Leaks

• Sub-steps:
  1. Inspect all vacuum lines for cracks or disconnections.
  2. Use a smoke machine or carburetor cleaner to test for leaks while the engine is running.
  3. Replace any damaged vacuum lines found during the inspection.