Starting System: Description and Operation

STARTING SYSTEM

The starting system consists of the following:
- Starter motor
- Starter solenoid
- Starter drive
- Starter relay
- Ignition switch
- Digital transmission range (TR) sensor
- Battery
- PCM
- One-touch integrated start (OTIS) diode

The function of the starting system is to crank the engine at a speed fast enough to permit the engine to start.

When the ignition switch is turned to the START position, current flows to the starter relay. On 4.0L SOHC engines, the current first goes through the TR sensor, and the PCM provides a ground for the starter relay. On 4.6L (3V) engines, if the transmission sends a signal to the PCM indicating a PARK or NEUTRAL position, the PCM will ground the starter relay. When the starter relay is energized, current flows to the starter solenoid.

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 flexplate ring gear. When the plunger is pulled all the way in, the 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 flexplate.

One-Touch Integrated Start (OTIS)
The vehicle is equipped with 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.

Once the ignition is turned to the START position and the vehicle is in NEUTRAL or PARK, the PCM reads starter motor request (SMR) from the ignition switch and gains control of the starter engagement. The customer is no longer in the loop after the initial crank request, and the customer may release the key to the RUN 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