how to fix P0303 code in 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

• Tools Required: OBD-II scanner, socket set, torque wrench, compression tester, multimeter, fuel injector tester, basic hand tools.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Spark Plug

• Remove the ignition coil from cylinder 3.
  • Use a socket to unscrew the coil bolts.
  • Lift the coil carefully to avoid damaging the connector.
• Remove the spark plug from cylinder 3.
  • Use a spark plug socket and a ratchet to unscrew the plug.
• Inspect the spark plug for fouling or wear. Replace if necessary.
• Install a new spark plug, ensuring the gap is set to manufacturer specifications (typically around 0.043 inches).

3. Test and Replace Ignition Coil

• Use a multimeter to test the resistance of the ignition coil.
  • If resistance is outside the manufacturer’s specifications, replace the coil.
• If replacing, install the new ignition coil onto cylinder 3.
  • Tighten it according to manufacturer specifications (usually around 7-10 Nm).

4. Inspect and Test Fuel Injector

• Disconnect the fuel injector connector from cylinder 3.
• Use a noid light to check for power at the connector while cranking the engine.
  • If there’s no signal, check wiring and ECM.
• If the injector is faulty, replace it using the following steps:
  • Remove the fuel rail if necessary, ensuring to relieve fuel pressure first.
  • Replace the old fuel injector with a new one and ensure proper seating.

5. Compression Test

• If misfire persists, perform a compression test on cylinder 3.
  • Insert the compression tester into the spark plug hole and crank the engine.
  • Note the compression reading; it should be within manufacturer specifications (usually above 150 psi).
• If compression is low, further investigation into valve or piston issues is necessary.