what causes P0303 misfire code in Toyota Highlander XU70 (2020-Present)

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool down before proceeding with repairs.

2. Inspect and Replace Spark Plug

• Step 1: Remove the engine cover if applicable (use a socket set).
• Step 2: Unscrew the spark plug wire or coil pack for cylinder 3.
• Step 3: Remove the spark plug using a spark plug socket and ratchet.
• Step 4: Inspect the spark plug for wear (carbon buildup, cracks, or damage). Replace if necessary with an OEM equivalent.
  • Torque Specification: Install the new spark plug and torque to 13 lb-ft (18 Nm).

3. Check and Replace Ignition Coil

• Step 1: If the spark plug is fine, inspect the ignition coil for cylinder 3.
• Step 2: Disconnect the electrical connector from the ignition coil.
• Step 3: Remove the ignition coil by unscrewing the retaining bolts.
• Step 4: Replace with a new ignition coil if faulty.
  • Torque Specification: Tighten the ignition coil bolts to the manufacturer’s specification (usually around 8 lb-ft or 11 Nm).

4. Inspect and Replace Fuel Injector

• Step 1: If the ignition coil is functioning, check the fuel injector by disconnecting its electrical connector.
• Step 2: Use a noid light to verify that the injector is receiving a signal.
• Step 3: If no signal, further diagnose the wiring harness; if signal is present, replace the fuel injector.
• Step 4: Install the new fuel injector and reconnect all connectors.