The electrical power behind your vehicle is generated from the Lexus Ignition Coil so the controlled explosion in the combustion chambers can occur on a continuous basis. Over the last decade the design and purpose of the ignition coil has changed on your Lexus engine. No longer does this engine component just produce the electrical charge that is sent to the spark plugs in one massive outlet through the distributor. With the removal of the distributor from the engine's makeup, the ignition coil now has to send each electrical impulse to every one of the cylinders your engine has individually.
The Lexus ignition coil is a sealed unit unlike the older style engines with a distributor. There is no cap or rotor that has to be cleaned or replaced during the routine tune-up. Because of this when the electrical charge from it is no longer sufficient to supply the necessary voltage to the spark plugs to operate you engine correctly, this ignition component has to be replaced.
The signal to send the correct voltage to each of the spark plugs is initiated from the onboard computer. This is the brains of your Lexus engine and must always be in proper working order. If it receives a faulty signal from any electrical component, like the ignition coil, the check engine light will become illuminated on the dash board of the vehicle. Each electrical component has its own code when it is faulty and they are stored in the memory of the computer so they can be retrieved. With the faulty ignition coil code retrieved, the battery has to be disconnected. This makes it safe to complete the repair procedure and remove the signal illuminating the check engine light from the dash board on your Lexus.