Starting System: Description and Operation

Starting System Components:

The starting system has:
- Ignition switch
- Starter relay
- Powertrain Control Module (PCM) double start override
- Neutral starting and back up switch with automatic transmissions only
- Wiring harness
- Battery
- Starter motor with an integral solenoid
- Positive Temperature Coefficient (PTC) is the circuit protection for the ignition feed to the starter relay coil. The PTC is located in the Junction Block.

These components form two separate circuits. A high amperage circuit that feeds the starter motor up to 300 + amps, and a control circuit that operates on less than 20 amps.

Supply Circuit and Control Circuit
The starter system consists of two separate circuits:
- A high amperage supply to feed the starter motor.
- A low amperage circuit to control the starter solenoid.

CIRCUIT OPERATION
The Power Distribution Center (PDC) supplies battery voltage to the engine starter motor solenoid through circuit T40 when the coil side of the engine starter motor relay energizes. Circuit A1 contains a 40 amp fuse (cavity 5), and feeds the contact side of the engine starter motor relay. Both the 40 amp fuse and the engine starter motor relay are located in the PDC.

Power for the coil side of the relay is supplied on circuit F45 when the ignition switch is moved to the START position Circuit F45 is protected by a 3 amp Positive Temperature Coefficient (PTC) located in PTC cavity 10 of the junction block. Power for the PTC is supplied on circuit A41. This circuit connects between the ignition switch and the PTC.

Circuit A1 supplies battery voltage for the A41 circuit when the ignition switch is in the START position. The A1 circuit is protected by a 40 amp fuse located in cavity 5 of the PDC.

Ground for the engine starter motor relay is supplied on circuit K90. This circuit connects from the relay to the Powertrain Control Module (PCM), cavity 8.

The PCM monitors the engine RPM and will remove the ground path for circuit K90 once the RPM has reached a predetermined level. This prevents the operator from over cranking the engine or attempting to crank the engine when it is running.

Circuit A0 (battery positive cable) supplies battery voltage to the engine starter motor when the solenoid energizes. Ground for the engine starter motor is supplied through the starter motor case.