Description & Operation

WARNING: Vehicles are equipped with air bag supplemental restraint system. Before attempting any repairs involving steering column, instrument panel or related components, see SERVICE PRECAUTIONS and DISABLING & ACTIVATING AIR BAG SYSTEM in appropriate AIR BAG RESTRAINT SYSTEMS article in ACCESSORIES & EQUIPMENT.

CAUTION: When battery is disconnected, vehicle computer and memory systems may lose memory data. Driveability problems may exist until computer systems have completed a relearn cycle. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION before disconnecting battery.

When ignition switch is turned to START position, battery voltage is applied to Park/Neutral Position (PNP) switch (A/T) or Clutch Pedal Position (CPP) switch (M/T). Current passes through PNP switch or CPP switch to starter solenoid only when vehicle is in Park or Neutral position (A/T) or clutch pedal is depressed (M/T). When voltage is applied to solenoid windings, this creates movement of solenoid plunger and shift lever, causing drive pinion to engage flywheel and close solenoid switch contacts. See Fig 1 . When solenoid switch contacts close, starter motor energizes and cranks the engine. As engine starts, pinion overrun clutch protects armature from excessive speed until ignition switch is opened and plunger return spring disengages pinion.

Fig 1: Typical Cranking Circuit Illustration

Courtesy of GENERAL MOTORS CORP.