GM Service Manual Online
For 1990-2009 cars only

Voltage is applied at all times to the ignition switch from Fuse 8 through the CKT 242 (RED) wire. When the ignition switch is turned to the START position, voltage is then applied from the CRANK fuse through the CKT 5 (YEL) wire. From the CRANK fuse, voltage is applied to the park/neutral position and backup lamp switch through the CKT 806 (PPL) wire. When the park/neutral position and backup lamp switch is placed in Park or Neutral, voltage is then applied to the coil of the starter relay through the CKT 1737 (YEL) wire. Since the starter relay is permanently grounded at G104 through the CKT 850 (BLK) wire, the relay will energize.

Voltage is applied at all times to the starter relay contacts from Fuse 8 through the CKT 242 (RED) wire. When the relay energizes, the relay contacts close, and voltage is then applied to the starter solenoid. Since the starter solenoid is permanently case grounded, the solenoid will energize two coils. The pull-in winding coil will energize to pull the starter solenoid contacts closed. When the contacts close, a plunger on the contacts will cause the pull-in winding coil circuit to open. Then the hold-in winding coil will hold the starter solenoid contacts closed. Voltage is then applied to the starter motor from the battery through the CKT 1 (BLK) wire and closed contacts of the starter solenoid. Since the starter motor is also permanently case grounded, the motor will run until the ignition switch is moved out of start position. When this happens, a spring in the starter solenoid will move the starter solenoid contacts and the plunger back to the rest position.