how to fix P0303 misfire code on my Toyota Corolla E140 (2006-2013)

Learn how to diagnose and fix P0303 cylinder 3 misfire in Toyota Corolla. Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

• Gather tools: OBD-II scanner, socket set, torque wrench, spark plug socket, compression gauge, multimeter, and vacuum gauge.
• Disconnect the negative battery terminal to ensure safety.

2. Inspect and Replace Spark Plug

• Sub-steps:
  1. Remove the engine cover if applicable.
  2. Disconnect the ignition coil connector for cylinder 3.
  3. Remove the ignition coil using the appropriate socket.
  4. Remove the spark plug with a spark plug socket.
  5. Inspect the spark plug for wear; replace if necessary with OEM equivalent (e.g., NGK or Denso).
  6. Install the new spark plug and torque it to manufacturer specifications (typically 13-15 lb-ft).
  7. Reinstall the ignition coil and reconnect the connector.

3. Test and Replace Ignition Coil

• Sub-steps:
  1. Swap the ignition coil from cylinder 3 with another cylinder (e.g., cylinder 1).
  2. Clear the error codes with the OBD-II scanner.
  3. Start the engine and monitor for the check engine light. If the P0303 code returns, proceed to replace the ignition coil.
  4. Install a new ignition coil (ensure it is compatible with the 2006-2013 Toyota Corolla) and torque to specifications.

4. Inspect and Test Fuel Injector

• Sub-steps:
  1. Disconnect the fuel injector connector for cylinder 3.
  2. Use a multimeter to test the electrical resistance of the injector (specifications typically around 12-16 ohms).
  3. If resistance is out of spec, replace the fuel injector with an OEM part.
  4. Reconnect the fuel injector and ensure proper seating.

5. Perform Compression Test

• Sub-steps:
  1. Remove all spark plugs to facilitate testing.
  2. Insert the compression gauge into the spark plug hole of cylinder 3.
  3. Crank the engine for several seconds and record the reading.
  4. Compare the reading to manufacturer specifications (should be around 180 psi).
  5. If compression is low, further inspection of the piston rings or valves may be necessary.