my Toyota Corolla E170 (2013-2019) has a check engine light and code P0301

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Replace Spark Plug

• Tools Required: Spark plug socket, ratchet, torque wrench
• Remove the ignition coil from cylinder 1 by unscrewing the retaining bolts.
• Remove the spark plug using the spark plug socket.
• Inspect and clean the spark plug hole to prevent debris from entering the cylinder.
• Install the new spark plug hand-tight and then torque it to 13 lb-ft (17.6 Nm).
• Reinstall the ignition coil and ensure it is secured properly.

3. Test and Replace Ignition Coil (if necessary)

• Use a multimeter to measure the resistance of the ignition coil. It should be within manufacturer specifications (typically around 0.4 - 0.6 ohms).
• If the ignition coil is out of spec, replace it with a new one.
• Reconnect the ignition coil harness and ensure it clicks into place.

4. Inspect Fuel Injector

• Tools Required: Noid light or stethoscope
• Disconnect the fuel injector connector.
• Use a noid light to check if the injector is receiving a signal. If not, check the wiring and ECM for faults.
• If the injector is not functioning, replace it with a new unit and reconnect the harness.

5. Conduct Compression Test

• Tools Required: Compression gauge
• Remove the spark plug from cylinder 1 and insert the compression gauge.
• Crank the engine to get a reading. It should be between 180-210 psi.
• If the pressure is low, further investigation may be needed for valve or piston issues.