my Toyota Highlander Fourth Generation (2020-present) has a check engine light and code P0301, what...

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the battery (negative terminal) to ensure safety during repairs.

2. Inspect and Replace Spark Plug

1. Remove the engine cover if applicable.
2. Locate cylinder 1 spark plug (typically the front left).
3. Using a spark plug socket, remove the spark plug.
4. Inspect the spark plug for signs of wear or fouling.
5. If damaged, replace with a new spark plug (specification: OEM or equivalent).
6. Torque the new spark plug to manufacturer specifications (usually around 13-16 lb-ft).

3. Check and Replace Ignition Coil

1. Disconnect the electrical connector from the ignition coil on cylinder 1.
2. Remove the mounting bolts securing the ignition coil.
3. Carefully remove the ignition coil from the spark plug.
4. Inspect the coil for cracks or damage; replace if necessary.
5. Install the new ignition coil and torque bolts to specification.
6. Reconnect the electrical connector.

4. Inspect and Test Fuel Injector

1. Disconnect the fuel injector connector on cylinder 1.
2. Remove the fuel rail if necessary to access the injector.
3. Test the injector with a multimeter for resistance (specification: 12-16 ohms).
4. Replace the injector if it does not meet specifications.
5. Reinstall the fuel rail and reconnect the fuel injector harness.

5. Compression Test

1. Remove the spark plug from cylinder 1.
2. Insert a compression gauge into the spark plug hole.
3. Crank the engine for a few seconds and record the pressure reading.
4. Compare the reading to the manufacturer's specifications (usually 120-220 psi).
5. If compression is low, further diagnostics on the engine internals may be needed.