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

Solution

1. Preparation

• Gather tools and parts needed for repair.
• Disconnect the negative battery cable to prevent electrical shorts.
• Allow engine to cool if it has been running.

2. Inspect and Replace Spark Plugs

• Tools Required: Socket set, torque wrench, spark plug socket
• Remove the engine cover if applicable.
• Disconnect the ignition coils from the spark plugs.
• Use the spark plug socket to remove the old spark plugs.
• Inspect the spark plugs for wear; replace with OEM specifications if needed (usually NGK or Denso).
• Torque new spark plugs to the manufacturer’s specifications (typically around 13-16 lb-ft).
• Reconnect the ignition coils.

3. Test and Replace Ignition Coils

• Tools Required: Multimeter, socket set
• Disconnect the ignition coils from the wiring harness.
• Test each ignition coil with a multimeter for proper resistance (consult service manual for specifications).
• If any ignition coils are out of specification, replace them with OEM parts.
• Reconnect wiring harness once tests are complete.

4. Check Fuel Injectors

• Tools Required: Fuel pressure gauge, injector cleaning kit (if needed)
• Disconnect the fuel injector connectors.
• Check fuel injector pulse using a noid light or oscilloscope.
• If injectors are clogged, use a fuel injector cleaning kit or replace them.
• Reconnect fuel injector connectors.

5. Inspect Vacuum Lines

• Tools Required: Visual inspection tools
• Visually inspect all vacuum lines connected to the intake manifold for cracks or disconnections.
• Replace any damaged vacuum lines to ensure proper air-fuel mixture.

6. Perform Compression Test

• Tools Required: Compression tester
• Remove spark plugs and install the compression tester in each cylinder.
• Crank the engine and record the compression readings for each cylinder.
• Compare readings to the manufacturer's specifications to check for internal engine issues.