GM Service Manual Online
For 1990-2009 cars only

The starter is a non-repairable starter motor. It has 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 battery voltage is removed from the starter solenoid S terminal. 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 (L61)

Moving the ignition switch to the START position applies 12 volts to the park/neutral position (PNP) switch if equipped with an automatic transmission or the clutch start switch if equipped with a manual transmission. When the automatic transmission is in the PARK or NEUTRAL position, 12 volts are applied to the S terminal of the starter. When the clutch is depressed for the manual transmission, 12 volts are applied to the S terminal of the starter. Ground is supplied through the engine block for either application.

Circuit Description (LAT)

Moving the ignition switch to the START position applies 12 volts to the coil side of the STARTER relay. The switch side of the STARTER relay has 12 volts applied at all times. The engine control module (ECM) verifies that all parameters are met for starting. The ECM then grounds the STARTER relay control circuit. When the STARTER relay is energized, 12 volts are applied to the S terminal of the starter. Ground is supplied through the engine block.

Circuit Description (L66)

Moving the ignition switch to the START position applies 12 volts to the coil and switch sides of the STARTER relay. When the PNP switch is in the PARK or NEUTRAL position, ground is applied by the PNP switch to the STARTER relay coil control circuit. When the STARTER relay is energized, 12 volts are applied to the S terminal of the starter. Ground is supplied through the engine block.