Operation

OPERATION

The starting electrical system is made up of two separate circuits: a high-amperage feed circuit that provides the starter motor with high-amperage battery voltage during cranking, and a low-amperage relay control circuit that provides approximately 20 amps of battery voltage to the starter solenoid. The high-amperage feed circuit components include the battery, the battery cables, the contact disc portion of the starter solenoid, and the starter motor itself. The low-amperage control circuit components include the Electronic Ignition Switch (EIS), the park/neutral position switch (automatic transmission), the starter relay, The PCM (or ECM, if equipped with a diesel engine), the control side of the starter solenoid, and the related wire harnesses.

The EIS is not hard wired, or directly wired to the starter control circuit. It communicates the switch position of the EIS to the PCM or ECM over the CAN-C bus. When the EIS is turned on, and then to the start position, the PCM or ECM will receive the ignition on and start signals from the EIS via the CAN-C bus, and the PCM or ECM will actuate the starter control relay, causing the starter solenoid to actuate the starter. Because the EIS and PCM will set DTCs, the first step to diagnosing any no-crank starter problems is to verify that there are no EIS, Drive Authorization System (DAS), or starter/engine control relay related DTCs. Refer to the appropriate engine or body electrical system diagnostic procedures for DTCs related to these starting system components.

If the vehicle is equipped with an automatic transmission, the EIS receives a signal via the CAN-C bus that indicates the position of the park/neutral position switch. This normally open switch prevents the EIS from enabling the PCM or ECM to actuate the starter relay and starter motor unless the automatic transmission gear selector is in the Neutral or Park positions.

When the starter relay coil is energized, the normally open relay contacts close. The relay contacts connect the relay common feed terminal to the relay normally open terminal. The closed relay contacts energize the starter solenoid coil windings.

The energized solenoid pull-in coil pulls in the solenoid plunger. The solenoid plunger pulls the shift lever in the starter motor. This engages the starter overrunning clutch and pinion gear with the starter ring gear on the manual transmission flywheel or on the automatic transmission torque converter or torque converter drive plate.

As the solenoid plunger reaches the end of its travel, the solenoid contact disc completes the high-amperage starter feed circuit and energizes the solenoid plunger hold-in coil. Current now flows between the solenoid battery terminal and the starter motor, energizing the starter.

Once the engine starts, the overrunning clutch protects the starter motor from damage by allowing the starter pinion gear to spin faster than the pinion shaft. When the driver releases the ignition switch to the On position, the starter relay coil is de-energized. This causes the relay contacts to open. When the relay contacts open, the starter solenoid plunger hold-in coil is de-energized.

When the solenoid plunger hold-in coil is de-energized, the solenoid plunger return spring returns the plunger to its relaxed position. This causes the contact disc to open the starter feed circuit, and the shift lever to disengage the overrunning clutch and pinion gear from the starter ring gear.