how to fix P0304 code on my Toyota Corolla E140 (2006-2013)

Learn how to diagnose and fix P0304 cylinder 4 misfire in Toyota Corolla. Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Spark Plug

• Sub-steps:
  1. Remove the ignition coil covering the spark plug for cylinder 4.
  2. Unplug the ignition coil connector.
  3. Remove the ignition coil using a socket set.
  4. Inspect the spark plug for wear, oil deposits, or damage.
  5. If necessary, replace the spark plug with a new one (OEM recommended).
  6. Reinstall the ignition coil and reconnect the electrical connector.

3. Test and Replace Ignition Coil

• Sub-steps:
  1. If the spark plug is fine, test the ignition coil for cylinder 4 using a multimeter (primary and secondary resistance tests).
  2. If the coil is faulty, replace it with a new ignition coil.
  3. Reinstall the ignition coil and reconnect the connector.

4. Inspect Fuel Injector

• Sub-steps:
  1. Disconnect the fuel injector connector.
  2. Remove the fuel injector from cylinder 4 using appropriate tools.
  3. Inspect the injector for clogs or damage.
  4. Clean or replace the fuel injector as necessary.
  5. Reinstall the injector, connecting the fuel line and electrical connector.

5. Perform Compression Test

• Sub-steps:
  1. Remove the spark plug from cylinder 4.
  2. Insert a compression gauge into the spark plug hole.
  3. Crank the engine to measure compression; compare to specifications (usually around 180-200 psi).
  4. If compression is low, investigate further for potential head gasket issues or valve problems.

Tools Required:

• OBD-II scanner
• Socket set
• Torque wrench
• Multimeter
• Compression gauge
• Fuel injector cleaner (if applicable)

Parts Required:

• Spark plug (specific to Toyota Corolla)
• Ignition coil (if required)
• Fuel injector (if required)
• Engine oil (for any necessary lubrication during assembly)

Estimated Repair Time: 2-4 hours

Safety Warnings:

• Disconnect battery before working on electrical systems.
• Allow engine to cool before starting work to prevent burns.