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Engine Speed Sensor

Engine speed signal comes from Hall Effect unit mounted above distributor on 2.5L engine and from terminal "R" of conventional HEI module in distributor on all other models. It is not "sensor" in that it is not separate component.

Pulses from distributor are sent to ECM where time between these pulses (dwell) is used to calculate engine speed. ECM sends spark advance modification signal back to distributor.

NOTE: See GENERAL MOTORS COMPUTER COMMAND CONTROL article in COMPUTERIZED ENGINE CONTROL section for further information.
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