Starting System: Description and Operation

Starting System

The starting system consists of the following:

- Starter motor
- Starter motor relay
- Transmission Range (TR) sensor
- Battery
- Ignition switch
- PCM
- Start diode

When the starter solenoid is energized, a magnetic field is created in the starter solenoid windings. The iron plunger core is drawn into the starter solenoid coil, and a drive lever and pin connected to the starter drive engages the drive pinion gear to the flywheel ring gear. When the plunger is pulled all the way in, its contact disc closes the circuit between the battery and the motor feed terminals. This sends current to the motor, and the drive pinion gear cranks the flexplate to start the engine. When current flows to the starter motor, the starter solenoid pull-in coil is bypassed, and the hold-in coil keeps the drive pinion gear engaged with the flywheel.

An overrunning clutch in the starter drive protects the starter motor from excessive speeds during the brief period before the driver releases the ignition switch from the START position as the engine starts.

The starting system uses a TR sensor located in the transmission. The TR sensor prevents operation of the starter motor unless NEUTRAL or PARK is selected. The vehicle has One-Touch Integrated Start (OTIS), a computer-assisted cranking system. This feature assists in starting the engine. If the ignition key is turned to the START position and released when the engine begins cranking, the engine may continue cranking for up to 10 seconds or until the vehicle starts.


One-Touch Integrated Start (OTIS)

Once the ignition is turned to the START position and the vehicle is in PARK or NEUTRAL, the PCM reads the starter motor request from the ignition switch and gains control of the starter engagement. The customer is no longer in the loop after the initial crank request, the customer may release the key to the RUN/START position. The PCM will disengage the starter motor based on the following events:

- The engine is started (rpm threshold)
- A set time has been exceeded (calibrated)
- The ignition key has been turned to the OFF position