For 1990-2009 cars

### System Operation

The Electronic Ignition (EI) system consists of two separate ignition coils, an electronic Ignition Control Module (ICM) and a secondary conductor housing mounted to an aluminum cover plate. A Crankshaft Position (CKP) sensor, related connecting wires and the Ignition Control (IC) portion of the PCM make up the remainder of the system.

A distributorless ignition system, such as this one, uses a waste spark method of spark distribution. Each cylinder is paired with the cylinder that is opposite it (1-4 or 2-3). The spark occurs simultaneously in the cylinder coming up on the compression stroke and in the cylinder coming up on the exhaust stroke.

The cylinder on the exhaust stroke requires very little of the available energy to fire the spark plug. The remaining energy will be used as required by the cylinder on the compression stroke. The same process is repeated when the cylinders reverse roles.

It is possible in a no load condition for one plug to fire even through the spark plug lead from the same coil is disconnected from the other spark plug. The disconnected spark plug lead acts as one plate of a capacitor, with the engine being the other plate. These two capacitor plates are charged as a current surge (spark) jumps across the gap of the connected spark plug. The plates are then discharged as the secondary energy is dissipated in an oscillating current across the gap of the spark plug still connected. Because of the direction of current flow in the primary winding and thus, in the secondary winding, one plug fires from the center electrode to the side electrode while the other fires from side electrode to center electrode.

This system utilizes the IC signal from the PCM to control spark timing. To properly control ignition timing, the PCM also relies on the following information:

• | Engine load (manifold pressure or vacuum).

• | Engine coolant temperature.

• | Intake air temperature.

• | Crankshaft position.

• | Engine speed (RPM).

• | Spark knock indication.

### Crankshaft Position (CKP) Sensor

Important: Perform a crankshaft position (CKP) system variation learn procedure any time you make a change to the crankshaft sensor to crankshaft relationship. Changing the crank sensor to crankshaft relationship will not allow the PCM to detect a misfire at all speeds and loads accurately. Resulting in possibly setting a false misfire DTC. Removing a part for inspection and then reinstalling the same part is considered a disturbance. A false DTC P0300 could set if you do not perform this procedure. Refer to Crankshaft Position System Variation Learn Procedure.CKP System Variation Learn Procedure in Engine Controls.

This system uses a magnetic CKP sensor, mounted remotely from the ICM, which protrudes into the block within approximately .050 in. of the crankshaft reluctor. The reluctor is a special wheel cast into the crankshaft with seven slots machined into it, six of which are equally spaced 60 degrees apart. A seventh slot, is spaced 10 degrees from one of the other slots and serves to generate a sync-pulse. As the reluctor rotates as part of the crankshaft, the slots change the magnetic field of the sensor, creating an induced voltage pulse.

Based on the CKP sensor pulses, the ICM sends 7X reference signals to the PCM which is used to indicate crankshaft position and engine speed. The ICM continues to send these reference pulse to the PCM at a rate of seven per 360 degrees of crankshaft rotation. This signal is called the 7X reference because it occurs 7 times per crankshaft revolution. The 7X reference signal is necessary for the PCM to determine when to activate the fuel injectors.

By comparing the time between pulses, the PCM can recognize the pulse representing the seventh slot, sync pulse, which starts the calculation of ignition coil sequencing. The second crank pulse following the sync pulse signals the PCM to fire the #2-3 ignition coil and the fifth crank pulse signals the PCM to fire the #1-4 ignition coil.

### Camshaft Position (CMP) Sensor

The camshaft position sensor (CMP) is used to correlate crankshaft to camshaft position so that the Powertrain Control Module (PCM) can determine which cylinder is ready to be fueled by the fuel injector. The CMP sensor is also used to determine which cylinder is misfiring when misfire is present. If the PCM receives an intermittent signal from the CMP, then the CMP resync counter will increment. When the PCM cannot use the information from the CMP sensor, a DTC is set and the PCM will fuel the engine using the alternating synchronous double fire (ASDF) method. This sensor has no effect on the EI system.

A malfunction in the CMP sensor circuits will cause a DTC P0341 or P0342.

### Ignition Coils

Two separate coils are mounted inside the housing. Each coil provides the spark for two plugs simultaneously (waste spark distribution). Each coil can also be replaced separately.

### Electronic Ignition Control Module (ICM)

The electronic ignition control module (ICM) monitors the CKP sensor signals and based on these signals, sends a 7X reference signal to the PCM so that correct spark timing and fuel injector control can be maintained during all crank and run conditions. Since the PCM controls spark timing and ignition control during crank and run, there is no bypass mode.

The ICM is not repairable. When a module is diagnosed to be faulty, it is replaced as a separate component.

### Ignition Control (IC)

This system uses the same circuits between the ICM and the PCM that distributor type systems use. Following is a brief description for each of the IC circuits.

• | Crankshaft position (CKP) sensor activity (7X reference)--The CKP sensor generates a signal to the ICM which results in a reference pulse, square wave signal, being sent to the PCM. The PCM uses this signal to calculate crankshaft position, engine speed and injector pulse width. The engine will not start or run if this circuit is open or grounded.

• | Reference Low-- his wire is grounded through the ICM and insures that the ground circuit has no voltage drop between the ICM and the PCM which could affect performance. The PCM compares voltage pulses on the 7X or reference input to those on this circuit, ignoring any pulses that appear on both. A pulse that appears on the reference low circuit alone is assumed to be caused by radio frequency interference (RFI).

• | Ignition control (IC) 1 & 2--The PCM sends the ignition control pulse to the ICM on these circuits. These signals are similar to the 7X reference pulse square wave except that the PCM uses sensor inputs to determine the pulse timing to control spark advance. When the PCM receives the 7X signal, it will determine which pair of cylinders will be fired (1 & 4 or 2 & 3). It then tells the ICM which cylinder to fire through the ignition control circuits.