Electronic Ignition System
The Electronic Ignition (EI) module, ignition coil housing with coil packs and spark plug boots are bolted as an assembly to the top of cam cover. The EI module charges and discharges the coils based on ECM control. The ECM uses a high control signal of about 5 volts to charge up the coil and a low control signal of about zero volts to discharge the coil. If coil is charged and the control signal is low, the coil will fire through its secondary towers. ECM controls spark timing and dwell (spark on-time) under all engine running conditions.
- Crankshaft Position Sensor (2.2L)
The Crankshaft Position (CKP) sensor is mounted on engine block, near starter. See Fig 1 . CKP produces an AC voltage of different amplitude (as high as 150 peak volts) and frequency depending on the velocity of the crankshaft. This AC voltage is sent to the ECM. The crankshaft has 7 machined notches, 6 of which are spaced 60 degrees apart. The remaining notch is 10 degrees before the No. 4 cylinder Top Dead Center (TDC) notch. The extra notch is used by the ECM to determine the position of the No. 4 cylinder which is necessary to synchronize engine position. The CKP sensor is used for fuel delivery, spark timing, misfire diagnostics and tachometer display. - Crankshaft Position Sensor (3.0L)
The Crankshaft Position (CKP) sensor is located on engine block, near oil filter housing. See Fig 2 . CKP sensor produces an AC voltage of different amplitude and frequency depending on the velocity of the crankshaft reluctor wheel. The crankshaft reluctor wheel contains 58 teeth (58X signal) that are 6 degrees apart with a 12-degree span that is uncut. This 12-degree span is used to locate the cylinder No. 1 top dead center piston position used for engine synchronization. CKP sensor in conjunction with the Camshaft Position (CMP) sensor can properly synchronize spark timing; fuel timing and spark knock control. As the reluctor wheel tooth rotates past the CKP sensor, the sensor's internal Hall Effect device pulls the signal circuit to ground. The ECM expects to see one high (12 volts) to low (zero volts) transition once every 2 crankshaft rotations as the reluctor tooth passes the sensor. The signal circuit should be at 12 volts at all times except when the transition occurs. If an error occurs in the CMP sensor circuit during the drive cycle, the ECM will continue to supply fuel and spark to the correct cylinder at the correct time until the ignition is turned off. If an error occurs in the CMP sensor circuit upon key-up, the ECM will default to supplying spark to both mating cylinders and enter non-sequential fuel injection. The engine may experience a 2-3 second extended crank, however, the engine will start and run. The large numbers of teeth on the reluctor wheel are used to correctly detect engine misfires. The ECM automatically learns the variation between all of the 58 teeth under 24 different engine speed/load ranges. To correctly detect misfires, the ECM will monitor the time it takes to pass 20 of the teeth (120 degrees of crankshaft rotation) after a cylinder has fired. If the time (based on engine speed and load) to pass the 20 teeth is too long, a cylinder misfire has occurred. - Ignition Coil
Each Electronic Ignition (EI) module is located directly over the cam cover. The EI system uses a coil over plug design to eliminate the need for spark plug wires. The El module houses the primary coils, secondary coils as well as drivers used to supply current to each of the primary coils. Each secondary coil fires independently of the others solely based on ECM control. The ECM sends a low current 5-volt control signal, which turns on a driver internal to the El module, allowing current to flow to one of the primary coils. The time the ECM holds the control signal high is called the dwell time. As the ECM turns off the control signal, the secondary coil will fire out of its secondary tower. The spark will travel down the spark plug boot, across the spark plug gap to ignite the cylinder air/fuel charge. The ECM uses independent control signals to fire each cylinder within that specific bank. - Ignition Control Module
The Ignition Control Module (ICM) receives ignition control signals from the ECM which in turn triggers the corresponding ignition coils. Since the ECM controls spark timing and ignition control during crank and run cycles, there is no by-pass mode. ICM is not serviceable.