how to address P0301 misfire code in Toyota Highlander Third Generation (2014-2019)

Solution

1. Preparation

• Gather tools and parts.
• Disconnect the negative battery terminal.
• Allow the engine to cool before starting work.

2. Inspect and Replace Spark Plug

• Tools Required: Socket set, torque wrench, spark plug socket.
• Sub-steps:
  1. Remove the engine cover if equipped.
  2. Disconnect the ignition coil connector from the spark plug.
  3. Unscrew the spark plug using the spark plug socket.
  4. Inspect the spark plug for wear or carbon buildup; replace if necessary.
  5. Install a new spark plug and torque it to the manufacturer’s specification (usually around 13 lb-ft).
  6. Reconnect the ignition coil connector.

3. Check and Replace Ignition Coil

• Tools Required: Socket set, multimeter.
• Sub-steps:
  1. Remove the ignition coil from cylinder 1 by unscrewing the mounting bolts.
  2. Test the ignition coil with a multimeter for primary and secondary resistance; replace if out of specification.
  3. Install a new ignition coil and secure it with bolts.
  4. Reconnect the ignition coil connector.

4. Inspect and Test Fuel Injector

• Tools Required: Noid light or multimeter.
• Sub-steps:
  1. Disconnect the fuel injector connector from cylinder 1.
  2. Using a noid light, check for injector pulse when the engine is cranked; replace injector if no signal.
  3. If testing with a multimeter, measure resistance; replace if outside the specified range (usually around 12-16 ohms).
  4. Install a new fuel injector if necessary and reconnect the connector.

5. Compression Test

• Tools Required: Compression gauge.
• Sub-steps:
  1. Remove the spark plug from cylinder 1.
  2. Insert the compression gauge into the spark plug hole.
  3. Crank the engine to take a reading; it should be within the manufacturer’s specifications (typically around 150-200 psi).
  4. If compression is low, further diagnosis may be required (valve issues, head gasket failure).