how to diagnose P0301 misfire code in my Toyota Highlander XU70 (2020-Present)?

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to ensure safety while working on electrical components.
• Allow the engine to cool before starting work.

2. Inspect and Replace Spark Plug

• Sub-steps:
  1. Remove the engine cover if applicable.
  2. Disconnect the ignition coil connector for cylinder 1.
  3. Unbolt and remove the ignition coil.
  4. Remove the spark plug using a spark plug socket and ratchet.
  5. Inspect the spark plug for wear or damage; replace if necessary (gapping according to manufacturer specifications).
  6. Reinstall the spark plug and torque to manufacturer specifications (typically around 13-15 lb-ft).
  7. Reinstall the ignition coil and connect the connector.

3. Test and Replace Ignition Coil (if needed)

• Sub-steps:
  1. If the spark plug is in good condition, test the ignition coil using an ohmmeter (consult specification for resistance values).
  2. If the coil is faulty, replace it with a new one.
  3. Reconnect the ignition coil and ensure it is secured properly.

4. Test Fuel Injector

• Sub-steps:
  1. Remove the fuel injector connector from cylinder 1.
  2. Connect a noid light to the injector harness to check for pulse.
  3. If no pulse is detected, inspect wiring or replace the injector; if pulse is detected, proceed to the next step.
  4. Replace the fuel injector if it is faulty, ensuring proper sealing.

5. Verify Compression

• Sub-steps:
  1. Remove the spark plug from cylinder 1.
  2. Insert a compression tester into the spark plug hole.
  3. Crank the engine and record the compression reading (should be within manufacturer specifications).
  4. If compression is low, inspect for possible internal damage or valve issues.