how to diagnose P0301 misfire code in Toyota Corolla E140 (2006-2013)

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the engine is cool before starting work.
• Disconnect the negative battery terminal for safety.

2. Inspect and Replace Spark Plug

• Sub-steps:
  • Remove the ignition coil cover if applicable.
  • Disconnect the ignition coil connector and remove the ignition coil from cylinder 1.
  • Remove the spark plug using a spark plug socket and ratchet.
  • Inspect the spark plug for wear; replace it if necessary.
  • Install a new spark plug, tightening to 13-15 lb-ft torque specifications.

3. Check and Replace Ignition Coil

• Sub-steps:
  • If the spark plug is in good condition, test the ignition coil with an ohmmeter for proper resistance.
  • If defective, replace the ignition coil with a new one.
  • Reattach the ignition coil connector and ensure it’s seated properly.

4. Perform Compression Test

• Sub-steps:
  • Remove the spark plug from cylinder 1 and screw in the compression tester.
  • Crank the engine for a few seconds and check the pressure reading.
  • Compare the reading to the manufacturer’s specifications (usually 150-200 psi).
  • If low, further investigate for potential issues like valve problems or head gasket failure.

5. Inspect and Clean Fuel Injector

• Sub-steps:
  • Remove the fuel injector connector from cylinder 1.
  • Use a multimeter to check the injector resistance; replace if out of specification.
  • If cleaning, use a fuel injector cleaning kit to clean the injector, or replace it if necessary.
  • Reconnect the fuel injector connector.