Starting System Description and Operation
The starter motors on this vehicle are non-repairable starter
motors. They have pole pieces that are arranged around the
armature. Both solenoid windings are energized. The pull-in winding
circuit is completed to the ground through the starter motor. The
windings work together magnetically to pull and hold in the
plunger. The plunger moves the shift lever. This action causes the
starter drive assembly to rotate on the armature shaft spline as it
engages with the flywheel ring gear on the engine. Moving at the
same time, the plunger also closes the solenoid switch contacts in
the starter solenoid. Full battery voltage is applied directly to
the starter motor and it cranks the engine.
As soon as the solenoid switch contacts close, current stops
flowing thorough the pull-in winding because battery voltage is
applied to both ends of the windings. The hold-in winding remains
energized; its magnetic field is strong enough to hold the plunger,
shift lever, starter drive assembly, and solenoid switch contacts
in place to continue cranking the engine. When the engine starts,
pinion overrun protects the armature from excessive speed until the
switch is opened.
When the ignition switch is released from the START position,
the starter relay opens and battery voltage is removed from the
starter solenoid. Current flows from the motor contacts through
both windings to the ground at the end of the hold-in winding.
However, the direction of the current flow through the pull-in
winding is now opposite the direction of the current flow when the
winding was first energized.
The magnetic fields of the pull-in and hold-in windings now
oppose one another. This action of the windings, along with the
help of the return spring, causes the starter drive assembly to
disengage and the solenoid switch contacts to open simultaneously.
As soon as the contacts open, the starter circuit is turned
off.
Circuit Description
When the ignition switch is placed in the Start position a
discrete signal is supplied to the body control module (BCM)
notifying it that the ignition is in the START position. The BCM
then sends a message to the engine control module (ECM) notifying
it that CRANK has been requested. The ECM verifies that the
transmission is in Park / Neutral. If it is, the ECM then supplies
12 V to the control circuit of the starter relay. When this occurs
battery positive voltage is supplied through the switch side of the
starter relay to the starter solenoid.
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