Coil On Plug System

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Individual COPs are mounted directly on spark plugs. See Figure. CKP sensor is used by PCM to indicate crankshaft position and speed by sensing a missing tooth on a pulse wheel mounted on front of crankshaft. The CMP sensor is used by PCM to identify when piston No. 1 is at Top Dead Center (TDC) of compression stroke. This signal is used to synchronize firing of individual coils.

The individual coils receive their signal from PCM to fire at a calculated spark target. Only one coil is fired at a time and only on compression stroke. PCM acts as an electronic switch to ground individual coil primary circuit. When the switch is closed, battery voltage applied to coil primary circuit builds a magnetic field around primary coil. When the switch opens, power is interrupted and primary field collapses, inducing high voltage in secondary coil winding and spark plug is fired. For additional COP information, see COIL ON PLUG under OUTPUT SIGNALS under COMPUTERIZED ENGINE CONTROLS.