Another ignition system that uses a magneto resistive crankshaft position sensor is the coil-near-plug system used on the LS1 engines starting in 1997. The coil-near-plug system consists of the following components/circuits:

Eight Ignition Coils/Modules

Eight Ignition Control (IC) Circuits

Camshaft Position (CMP) Sensor

.5X Camshaft Reluctor Wheel

Crankshaft Position (CKP) Sensor

24X Crankshaft Reluctor Wheel

Related Connecting Wires

Powertrain Control Module (PCM)

Crankshaft Position Sensor and Reluctor Wheel
The dual magneto resistive Crankshaft Position (CKP) sensor is located in the right rear of the engine, behind the starter. The CKP sensor works with a 24X reluctor wheel.
The reluctor wheel is mounted on the rear of the crankshaft. The 24X reluctor wheel has two different width notches that are 15 degrees apart. This Pulse Width Encoded pattern allows cylinder position identification within 90 degrees of crankshaft rotation. In some cases, cylinder identification can be located in 45 degrees of crankshaft rotation. The reluctor wheel also has dual track notches that are 180 degrees out of phase. The dual track design allows for quicker starts and accuracy.

The CKP signal must be available for the engine to start. The CMP signal is not needed to start and operate the engine. The PCM cannot determine when a particular cylinder is on either compression or exhaust stroke by the 24X signal. The CMP sensor is used to determine what stroke the engine is on. If the Cam Sensor fails, the system will attempt synchronization by firing one of two companion cylinders, and look for an increase in the RPM. An increase in the RPM signal indicates that the correct cylinder was fired, and the engine has started. If the PCM does not detect an increase RPM signal, a re-sync will occur to the opposite cylinder. A slightly longer cranking time may be a symptom of this condition.

Camshaft Position Sensor
The Camshaft Position (CMP) sensor is mounted through the top of the engine block at the rear of the intake valley cover. The CMP sensor works in conjunction with a .5X reluctor wheel. The reluctor wheel is located at the rear of the camshaft. The CMP sensor is used to determine whether a cylinder is on the compression or the exhaust stroke. As the camshaft rotates, the reluctor wheel interrupts a magnetic field produced by a magnet within the sensor. The CMP sensor internal circuitry detects this and produces a square-wave signal which is used by the PCM. The PCM uses this signal in combination with the CKP 24X signal to determine crankshaft position and stroke.

Ignition Coils/Modules

The coil-per-plug system has eight ignition coils/modules individually mounted above each cylinder on the rocker covers. The secondary ignition wires are short compared with a distributor ignition system wire. The coils/modules are fired sequentially. There is an Ignition Control (IC) circuit for each ignition coil/module. The eight ignition control circuits are connected to the PCM. All timing decisions are made by the PCM, which triggers each coil/module individually. The ignition coil/modules have the following circuits attached to them:

Ignition Feed Circuit
Ignition Control Circuit
Ground Circuit
Reference Low Circuit
The ignition feed circuits are fused separately for each bank of the engine. The two fuses also supply the injectors for that bank of the engine. Each coil/module is serviced separately.

This system puts out very high ignition energy for plug firing. Because the ignition wires are shorter, less energy is lost to ignition wire resistance. Furthermore, no energy is lost to the resistance of a waste spark system.