Integrated Electronic Ignition (EI) System

WARNING: This page is about a different car, the 2007 Mercury Mariner and 2007 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.

The EI system consists of a crankshaft position (CKP) sensor, coil(s) on plug (COP), and the PCM. The COP integrated EI system uses a separate coil per spark plug, and each coil is mounted directly onto the plug. The COP integrated EI system requires input from the camshaft position (CMP) sensor. Operation of the components are as follows:

NOTE: Electronic ignition engine timing is entirely controlled by the PCM. Electronic ignition engine timing is NOT adjustable. Do not attempt to check base timing. You will receive false readings.

The CKP sensor is used to indicate crankshaft position and speed by sensing a missing tooth on a pulse wheel mounted to the crankshaft. The CMP sensor is used by the COP integrated EI system to identify the top dead center (TDC) of compression of cylinder 1 to synchronize the firing of the individual coils.
The PCM uses the CKP signal to calculate a spark target and the CMP signal to identify the TDC of compression of cylinder 1 to synchronize the firing of the individual coils.
The COPs receive their signal from the PCM to fire at a calculated spark target. The COP system fires only one spark plug per coil and only on the compression stroke.
The PCM acts as an electronic switch to ground in the coil primary circuit. When the switch is closed, battery positive voltage (B+) applied to the coil primary circuit builds a magnetic field around the primary coil. When the switch opens, the power is interrupted and the primary field collapses inducing the high voltage in the secondary coil windings and the spark plug is fired. A kickback voltage spike occurs when the primary field collapses. The PCM uses this voltage spike to generate an ignition diagnostic monitor (IDM) signal. IDM communicates information by pulse width modulation in the PCM.
The PCM processes the CKP signal and broadcasts it to the communication network. The PCM also sends it to the transaxle control module (TCM) as a hardwired clean tachometer output (CTO) signal.

Fig 1: Typical COP Ignition System
Courtesy of FORD MOTOR CO.