what does code P0303 mean for my Toyota Highlander

Solution

1. Preparation

• Gather tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool down before beginning work.

2. Inspect and Replace Spark Plug

• Remove the ignition coil from cylinder 3.
• Use a spark plug socket to remove the spark plug from cylinder 3.
• Inspect the spark plug for signs of wear or fouling; replace with a new spark plug if necessary.
• Install the new spark plug and torque to the manufacturer’s specifications (usually around 13-15 lb-ft).

3. Check and Replace Ignition Coil

• If the spark plug is in good condition, test the ignition coil using a multimeter:
  • Measure the primary resistance across the coil terminals; compare with the specifications in the service manual.
  • If not within specifications, replace the ignition coil for cylinder 3.
• Reinstall the ignition coil and ensure it is securely connected.

4. Compression Test (If Needed)

• Remove the spark plug from cylinder 3 and install a compression gauge.
• Crank the engine several times to obtain a compression reading.
• Compare the reading to specifications; if significantly low, further diagnostics may be required for potential internal engine issues.

5. Fuel Injector Inspection (If Needed)

• If misfire persists, remove and inspect the fuel injector for cylinder 3.
• Clean the fuel injector using a fuel injector cleaning kit or replace it if clogged or faulty.
• Reinstall the fuel injector and reconnect any associated wiring.