how to fix P0303 misfire code in my Toyota Highlander

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the battery to prevent electrical shorts.
• Safety goggles and gloves should be worn.

2. Inspect and Replace Spark Plug

• Tools Required: Spark plug socket, ratchet, torque wrench
• Remove the ignition coil from cylinder 3.
• Carefully remove the spark plug using the spark plug socket.
• Inspect the spark plug for wear or damage (e.g., fouling, cracking).
• If damaged, replace with a new spark plug, ensuring it is gapped correctly (typically around 0.043 inches for most Toyota engines).
• Reinstall the ignition coil and reconnect the electrical connector.

3. Inspect and Replace Ignition Coil

• If the spark plug appears to be in good condition, test the ignition coil.
• Tools Required: Multimeter
• Use a multimeter to check the primary and secondary resistance of the ignition coil according to the specifications in the vehicle service manual.
• If the coil is faulty, replace it with a new one.
• Reinstall and reconnect as necessary.

4. Check and Replace Fuel Injector (if necessary)

• Tools Required: Noid light, fuel injector removal tool
• Use a noid light to check for proper operation of the fuel injector for cylinder 3.
• If the injector does not activate, remove it using the fuel injector removal tool and clean it.
• If cleaning does not resolve the issue, replace the fuel injector with a new one.

5. Compression Test

• If misfire persists, perform a compression test to assess the health of cylinder 3.
• Tools Required: Compression gauge
• Remove the spark plug from cylinder 3 and install the compression gauge.
• Crank the engine to get a reading. It should be within the manufacturer's specifications (typically 150-200 psi).
• If compression is low, further investigation into potential internal engine issues may be required.