Controlled Power Feeds

CONTROLLED POWER FEEDS

Front Airbag System
The FCM provides power to the Occupant Restraint Control (ORC) system through two "fuseless" circuits (ORC RUN/START, and ORC RUN only). These circuits are electronically controlled and continuously monitored for malfunctions. Power is supplied while the ignition switch is in the RUN and START positions on pin 48 of the FCM connector, and in the RUN only position on pin 29.

Side Airbag System
The FCM provides power to the Side Impact Airbag Control Module (SIACM) system through one "fuseless" circuit. This circuit is electronically controlled and continuously monitored for malfunctions. Power is supplied in the ignition RUN and START positions on pin 28 of the FCM connector.

Headlamp Power
The headlamp switch is a direct input to the BCM. The BCM sends a PCI Bus message to the FCM informing it of a headlamp switch status change. The FCM then turns on power to the headlamps through four "fuseless" circuits. These circuits are electronically controlled and continuously monitored for malfunctions. Power is supplied to each filament in a separate circuit (RH low on pin 6, RH high on pin 4, LH low on pin 3 and LH high on pin 5). For vehicles equipped with Daytime Running Lamps (DRL), the FCM electronically steps down the headlamp voltage to provide the desired illumination.

EATX Power
The electronic automatic 4 speed transmission module is powered when the ignition switch is in the UNLOCK, RUN or START positions. This circuit is electronically controlled and continuously monitored for malfunctions. Power is supplied through pin 27 of the FCM connector.

Front Washer Motor
The front washer switch is a direct input to the BCM. The BCM sends a PCI Bus message to the FCM informing it of a request to wash. The front washer motor is then powered through low side control inside the FCM. This circuit is electronically controlled and continuously monitored for malfunctions. In addition, the FCM electronically protects the washer motor from system voltages higher than 16 volts by automatically switching off the low side circuit. The low side circuit is connected to pin 45 in the FCM connector.

Rear Washer Motor
The rear washer switch is a direct input to the BCM. The BCM sends a PCI Bus message to the FCM informing it of a request to wash. The rear washer motor is then powered through low side control inside the FCM. This circuit is electronically controlled and continuously monitored for malfunctions. In addition, the FCM electronically protects the washer motor from system voltages higher than 16 volts by automatically switching off the low side circuit. The low side circuit is connected to pin 46 in the FCM connector.

Cabin Heater
When the ignition is in Run, the FCM monitors the PCI bus for the Cabin Heater Activation request. The Automatic or Manual Temperature Control initiates this request only when all conditions for the Cabin Heater activation are favorable. The request carries the status bit that the FCM requires to activate its Cabin Heater Assist Control output. This output is a low side driver (coming from FCM pin 15) which supplies a ground signal to the Cabin Heater (pin 5). When the Cabin Heater receives this ground signal input, it interprets this as an activation signal. The FCM low side driver is also capable of diagnostic sensing. The driver will sense an open circuit when the driver is off, and will sense a short to voltage when the driver is on. The FCM will set DTCs for both of these types of faults. For additional information, refer to Cabin Heater under General Information and Diagnostic Procedures in the manual.

Brake Shift Interlock System
The brake shift interlock solenoid receives power from both high side and low side controls inside the FCM. The high side control is on the same circuit as the EATX module power, and the low side control comes through pin 47 of the FCM connector. The solenoid is controlled by the low side driver when the brake pedal is pressed. Both circuits are continuously monitored for malfunctions.