See Figures 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10
The engines covered by this guide employ distributorless ignition systems. The distributorless ignition system is referred to as the Direct Ignition System (DIS). This system's three main components are the coil pack, the crankshaft sensor, and the camshaft sensor. The crankshaft and camshaft sensors are hall effect devices. These devices use the change in a magnetic field (from an internal magnet) to sense whether a slot is present on the camshaft sprocket or a window is present on the torque converter driveplate. When a slot or window is present, the sensors switch input voltage from high (5.0 volts) to low (less than 0.3 volts). As the slot or window passes, the input voltage is switched back to high (5.0 volts). These changes in input voltage allow the engine controller to compute engine speed, crankshaft position, and camshaft position.
The ignition system is regulated by the Powertrain Control Module (PCM). The PCM supplies battery voltage to the ignition coil through the Auto Shutdown (ASD) relay. The PCM also controls the ground circuit for the ignition coil. By switching the ground path for the coil on and off, the PCM adjusts the ignition timing to meet changing engine operating conditions.
During the crank-start period the PCM advances ignition timing a set amount. During engine operation, the amount of spark advance provided by the PCM is determined by these input factors:
The PCM also regulates the fuel injection system.
The camshaft position sensor provides fuel injection synchronization and cylinder identification information. The sensor generates pulses that are the input sent to the PCM. The PCM interprets the camshaft position sensor input (along with the crankshaft position sensor input) to determine crankshaft position. The PCM uses the crankshaft position sensor input to determine injector sequence and ignition timing.
The camshaft position sensor determines when a slot in the camshaft gear passes beneath it. When metal aligns with the sensor, voltage drops to less than 0.5 volts. When a notch aligns with the sensor, voltages jumps to 5.0 volts. As a group of notches pass under the sensor, the voltage switches from low to high then back to low. The number of notches determine the amount of pulses.
The camshaft position sensor is mounted in the front of the timing case cover. The bottom of the sensor is positioned above the camshaft sprocket. The distance between the bottom of the sensor and the camshaft sprocket is critical to the operation of the system.
The crankshaft position sensor senses slots cut into the transaxle driveplate extension. There are 3 sets of slots. Each set contains 4 slots, for a total of 12 slots. Basic timing is set by the position of the last slot in each group. Once the PCM senses the last slot, it determines crankshaft position (which piston will next be at TDC) from the camshaft position sensor input. The 4 pulses generated by the crankshaft position sensor represents the 69°, 49°, 29 and 9° BTDC marks. It may take the PCM one engine revolution to determine crankshaft position during cranking.
The PCM uses the camshaft position sensor to determine injector sequence. The PCM determines ignition timing from the crankshaft position sensor. Once the crankshaft position has been determined, the PCM begins energizing the injectors in sequence.
The crankshaft position sensor is located in the transaxle housing. The bottom of the sensor is positioned next to the driveplate. The distance between the bottom of the sensor and the driveplate is critical to the operation of the system.
The coil assembly consists of 3 coils molded together. The assembly is mounted on the intake manifold. The number of each coil appears on the front of the coil pack.
High tension leads route to each cylinder from the coil. The coil fires two spark plugs every power stroke. One plug is the cylinder under compression, the other cylinder fires on the exhaust stroke. The PCM determines which of the coils to charge and fire at the correct time.
Coil one fires cylinders 1 and 4, coil two fires cylinders 2 and 5, and coil three fires cylinders 3 and 6. The coil's low primary resistance allows the PCM to fully charge the coil for each firing.