Starting System: Description and Operation

Starting System

The starting system consists of the following components:

- PCM (located on the RH side of cowl)
- Starter motor
- Ignition switch
- Digital Transmission Range (TR) sensor (automatic transmission-equipped vehicles) (located on the LH side of the transmission)
- Clutch Pedal Position (CPP) switch (manual transmission-equipped vehicles) (located on the clutch pedal)
- Starter motor relay (located in the Battery Junction Box (BJB))
- Batteries
- Battery cables
- Start diode (part of the One-Touch Integrated Start (OTIS) system) (located in the BJB)

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 flywheel 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.

Vehicles equipped with a manual transmission have a Clutch Pedal Position (CPP) switch mounted on the clutch pedal bracket. The CPP switch prevents operation of the starter motor unless the clutch pedal is fully depressed.

Vehicles equipped with an automatic transmission have a digital TR sensor. The digital TR sensor prevents operation of the starter motor unless the transmission is in NEUTRAL or PARK.


One-Touch Integrated Start (OTIS)

Only automatic transmission vehicles have 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, the PCM reads 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
- The ignition key has been turned to the OFF position