how to diagnose P0301 misfire code in Toyota Corolla E170 (2013-2019)

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, multimeter, compression tester, timing light, noid light.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the negative battery terminal to prevent any electrical issues.

2. Inspect and Replace Spark Plug

• Remove the ignition coil from cylinder 1.
• Remove the spark plug using a socket and ratchet.
• Inspect the spark plug for wear, carbon buildup, or damage; replace if necessary.
• If replacing, torque the new spark plug to the manufacturer’s specifications (typically around 13 lb-ft).
• Reinstall the ignition coil.

3. Test and Replace Ignition Coil (if necessary)

• Use a multimeter to check the resistance of the ignition coil.
• If the resistance is out of specification, replace the ignition coil with a new one.
• Reinstall the ignition coil and reconnect all wiring harnesses.

4. Check and Replace Fuel Injector (if necessary)

• Disconnect the fuel injector connector for cylinder 1.
• Test the injector with a noid light to ensure it is receiving a signal.
• If the injector does not pulse, replace it with a new one.
• If replacing, ensure to torque any mounting screws to the manufacturer’s specifications.

5. Perform Compression Test

• With the spark plug removed from cylinder 1, connect the compression tester.
• Crank the engine and note the reading; it should meet manufacturer specifications (typically around 150-200 psi).
• If the compression is low, further engine diagnosis may be required.

6. Final Steps

• Reconnect the battery terminal.
• Clear the trouble codes using the OBD-II scanner.
• Start the engine and check for the absence of the misfire code.