146 Auto Engine Performance and Driveability Copyright by Goodheart-Willcox Co., Inc. of many solid-state electronic components—diodes, transistors, capacitors, and resistors—in a single, sealed unit. Modules cannot be repaired and must be replaced if defective. In a coil-on-plug ignition system, an ignition control module is often located on top of each coil. In waste spark systems, the ignition control module may serve as the base for, or is part of, the ignition coil pack assembly, Figure 8-7. On many ignition systems, the ignition control module is incorporated into the ECM. On distributor-type ignition the same amount of voltage. These are sometimes called pencil coils. Figure 8-6 shows a cross-section of a pencil coil. These coils are often used where clearances are tight, such as between two camshaft covers of a dual overhead camshaft engine. Some pencil coils are installed for appearance only. Ignition Control Module The ignition control module is the solid-state device that processes inputs from sensors and other ignition com- ponents and collapses the coil’s magnetic field to produce a high voltage. Ignition control modules are composed Figure 8-4. In a distributorless ignition system, there is one coil for every two cylinders. Each coil fires two spark plugs at the same time. One of the two plugs fired by a coil does so on the cylinder’s exhaust stroke. Coils Figure 8-5. This direct ignition coil assembly consists of a coil, an ignition module, and a spark plug boot. Note that a spark plug is installed in the boot. (General Motors) Spark plug Boot Coil assembly Ignition module Figure 8-2. The iron core extends around the coils of the flat coil to increase the magnetic field interaction. A—Secondary output (+). B—Secondary output (–). C—Iron core. D—Primary winding. E—Secondary winding. (Mercedes-Benz) A B E D C Figure 8-3. The flat coil is installed near the distributor to reduce the amount of wire needed to connect the two components. Flat coil