GM Service Manual Online
For 1990-2009 cars only

Starter Circuit Operation

Battery voltage is available at the Ignition Switch and the Starter Relay contacts at all times through the RED (242) wire from the IGN-A fuse in the Underhood Fuse-Relay Center. Placing the Ignition Switch in START closes contacts to apply voltage on the YEL (5) wire to the Park/Neutral Position Switch. If the Automatic Transmission is in either Park or Neutral, voltage is applied from the YEL (1737) wire to the Starter Relay coil. The Starter Relay coil is grounded at Ground G103 by the BLK (150) wire. With voltage applied to the coil, the Starter Relay energizes. Voltage is then applied to the Starter Solenoid Winding Terminal S through the PPL (6) wire. Battery voltage is also available at all times through the BLK (1) wire at Starter Solenoid Terminal B. With battery voltage applied at Starter Solenoid Terminal S, current flows though the Hold-In Winding to the mechanical ground at the solenoid. Simultaneously, current flows through the Pull-In Winding and the Starter Motor to the Starter Motor's mechanical ground. The combined force of these windings overcomes the force of the Return Spring and pulls the starter's Plunger to engage the starter with the Flywheel Drive Assembly though the Shift Lever. The engine starts to turn over. The Plunger actuation also operates a contact in the Starter Solenoid which closes to apply battery voltage directly to the Starter Motor. With battery voltage applied directly to the Starter Motor, the Pull-In Winding no longer has a voltage drop across the coil and current ceases to flow. The Starter Solenoid remains engaged due to the current flow through the Hold-In Winding alone. The Starter motor continues to operate until the Ignition Switch is returned to the RUN position. With the Ignition Switch now in the RUN position, voltage is removed from Starter Solenoid Terminal S. However, voltage is still present at Terminal B. Both the Hold-In Winding and the Pull-In Winding are energized by battery voltage from the BLK (1) wire. However, the forces from these windings now oppose one another and the Plunger returns to the disengaged position through the operation of the Return Spring. This operates the contact to remove battery voltage from the Starter Motor and the motor stops. Both windings also de-energize. This Plunger operation also retracts the starter from the Flywheel Drive Assembly and the engine operates on its own power.