how to diagnose P0301 misfire code on Toyota Highlander Third Generation (2014-2019)

Solution

1. Preparation

• Gather tools and materials.
• Disconnect the vehicle's battery to ensure safety while working on electrical components.

2. Replace Spark Plug

• Tools Required: Spark plug socket, ratchet, torque wrench
• Remove the ignition coil from cylinder 1.
• Using a socket, remove the spark plug from cylinder 1.
• Inspect the old spark plug for signs of fouling or damage.
• Install a new spark plug, ensuring it is gapped according to manufacturer specifications (usually around 0.043 inches).
• Torque the new spark plug to the manufacturer’s specification (typically around 13 lb-ft).

3. Inspect/Replace Ignition Coil

• Tools Required: Socket set
• Remove the ignition coil from cylinder 1.
• Test the ignition coil with a multimeter to ensure it meets resistance values (typically 0.5 to 0.7 ohms for primary and 6.0 to 12.0 k ohms for secondary).
• If faulty, replace the ignition coil with a new one.
• Reinstall the ignition coil and ensure it is properly seated.

4. Test/Replace Fuel Injector

• Tools Required: Fuel pressure gauge, injector cleaning kit (if necessary)
• Connect a fuel pressure gauge to the fuel rail to ensure fuel pressure is within specifications (typically around 50-60 psi).
• If pressure is low, inspect the fuel filter and pump.
• If the injector is suspected to be clogged, use an injector cleaning kit or replace the fuel injector.

5. Compression Test (if needed)

• Tools Required: Compression gauge
• Remove the spark plug from cylinder 1.
• Insert the compression gauge into the spark plug hole.
• Crank the engine and record the compression reading; compare it with manufacturer specifications (should be around 180 psi).
• If readings are low, further investigation for internal engine issues may be needed.