Starting System: Description and Operation

The starting system consists of the following components:
^ starter motor
^ starter switch, part of the ignition switch
^ Digital Transmission Range (DTR) sensor (automatic transmission-equipped vehicles)
^ starter motor relay
^ starter solenoid
^ starter drive

Starter Motor:

Starter Motor
^ is a wound field, gear reduction, 12V DC motor.
^ has an integral starter solenoid.
^ has an overrunning clutch in the starter drive.

It functions as follows:
^ When the key cylinder turns to the start position, current flows through the solenoid pull-in and hold-in coils until the solenoid plunger is at the end of its travel. The plunger pulls the lever, which pushes the pinion to engage with the flywheel.
^ The contact bridges the solenoid terminals that bypass the pull-in coil. This allows the hold-coil to keep the starter drive engaged and to pass battery current to the starter motor. The starter motor cranks the engine fast enough to start it.
^ As the key returns to the RUN position, the relay cuts off current to the solenoid. The solenoid disengages the pinion from the flywheel.

Starter Relay
The starter interrupt relay consists of:
^ pull-in coil and contacts.

When the key cylinder is in the START position:
^ the pull-in coil is activated and pulls the contacts together.
^ current passes through the starter relay from the engine compartment power distribution box to the starter solenoid.

When the key cylinder is returned to the RUN position:
^ the relay turns off the starter solenoid which disengages the pinion from the flywheel.

Transmission Range Sensor (Automatic Transmission)
The transmission range sensor:
^ prevents starter motor engagement unless the transmission is in the NEUTRAL or PARK position.

Starter Drive
The starter drive:
^ is operated by the starter solenoid.
^ engages the flywheel to turn the engine.
^ has an internal overrunning clutch to disengage the starter motor when the engine starts.

Starter Motor, Disassembled View:

Starter Solenoid
The starter solenoid:
^ is an electromagnet.
^ engages the starter drive to the flywheel.
^ when energized, contacts close, connecting the battery to the starter motor and causing the starter motor to turn the starter drive.
^ is kept in the energized condition by a hold-in winding until the starter switch is released.

Air Intake Heater Element:

Air Intake Heater Relay Switch:

Intake Air Heater Starting Aid System
The intake air heater starting aid system improves cold weather starting and reduces white smoke and odor during cold weather starting and on extended idles.

The intake air heater starting aid system consists of the following:
^ Engine Oil Temperature (EOT) sensor
^ intake air heater relay switch
^ intake air heater element
^ Intake Air Temperature (IAT) sensor
^ Powertrain Control Module (PCM)
^ starter switch

Intake air heater starting aid system operation.
^ The system is activated by the PCM when the ambient air temperature is below 0°C (32°F), the engine oil temperature is below 55°C (131°F) and the battery voltage is above 11.7 volts.
^ The intake air heater will stay on for 30 minutes as long as the engine is idling and the above conditions are met.
^ The intake air heating system will only activate once per "key on event". If the heater is activated and the vehicle is driven, the heater will not activate if the vehicle is taken back to idle.
^ The intake air is heated by using a heating element mounted into the compressor manifold.
^ The intake air heater relay switch, located next to the glow plug relay switch, supplies power to the intake air heater element.