P0303 cylinder misfire , check engine light on

@canadiansamosa actually your P0303 Code means you have a Cylinder 3 Misfire. Now, there are a whole bunch of areas you would need to check:

• Open or short in engine wire harness

• Connector connection

• Vacuum hose connections

• Ignition system

• Injector

• Fuel pressure

• MAF meter

• ECT sensor

• Compression pressure

• Valve clearance

• Valve timing

• PCV valve and hose

• PCV hose connections

• ECM

since you only show the one cylinder misfiring, I would start with new spark plugs and replace the ignition coils. Then re-evaluate. Here is how to change the coils and here is the part from the Toyota Manual that deals with the Toyota Matrix ENGINE CONTROL SYSTEM and thus with your P0303 code. Let us know how this works out.