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Final Drive Control Module - Operation






OPERATION

POWER UP/DOWN

The Final Drive Control Module (FDCM) will power up with an OFF/ON transition of the hardwired ignition switch input, or with the presence of active CAN C communications.

The FDCM will power down when the vehicle ignition switch transitions from ON to OFF, or there are no CAN C messages, or there are no system requirements that dictate the controller to remain active

START-UP DIAGNOSTICS

When the FDCM is activated, the internal circuitry will undergo a diagnostic procedure. The controller will examine all inputs and outputs for short circuits to ground, short circuits to battery and open circuits and will also verify proper CPU and memory operation. If a fault is detected, a message will be sent out over the CAN C bus to the Cluster based Electronic Vehicle Information Center EVIC indicating that service is recommended.

After passing all diagnostic tests, the controller will receive and process inputs and produce the appropriate outputs. Proper monitoring of the controller inputs and outputs performance will continue.

INPUTS/OUTPUTS

The following are inputs to the FDCM:

- Lateral Accelerometer
- Transfer Case Range Select Switch
- Transfer Case Mode Sensor Signal
- 3 Direct Battery Feeds
- Ignition RUN Sense
- Sensor Grounds
- Module Grounds
- CAN C Bus

The following are outputs of the FDCM:

- 5V Sensor Supply
- Transfer Case NEUTRAL Lamp
- Front Electronic Limited Slip Differential Pressure Solenoid
- Rear Electronic Limited Slip Differential Pressure Solenoid
- Transfer Case Bi-directional Motor Control (A AND B)
- Switched B+ Solenoid Supply
- Transfer Case Motor Brake Control

TRANSFER CASE RANGE SELECT SWITCH INPUT (NEUTRAL AND 4HI/4LO SELECT SWITCH)

The FDCM will support circuitry which interfaces to the system's Transfer Case Range Select Switch, including a Transfer Case Range Select Switch voltage supply and a Transfer Case Range Select Switch input. The purpose of this circuitry is to determine the mode currently being requested by the operator via the resistance ladder network in the shifter assembly, where the Transfer Case Range Select Switch is packaged.

The NEUTRAL Select Switch Input will provide the operator with the ability to place the Transfer Case in Neutral. The 4HI/ 4LO Select Switch Input will provide the operator with the ability to place the transfer case in 4HI or 4LO. The NEUTRAL Select Switch is a momentary contact switch and the 4HI/4LO Select Switch is a 2-position toggle or a momentary contact switch and both these switches are provided through a resistor network for diagnostic purposes. The input will have an internal 1.0K +/- 1% pull-down resistor to ground.

As the selected position in the 4HI/4LO Switch varies and/or the NEUTRAL Switch is depressed or not, the resistance between the module's Transfer Case Range Select Switches voltage supply and Transfer Case Range Select Switches input will vary. Hardware, software, and calibrations within the FDCM will be provided that interpret the external resistance between the module's Transfer Case Range Select Switches voltage supply and Transfer Case Range Select Switches inputs as given in the table below:






NOTE: There is no requirement for the FDCM to distinguish between a neutral request from the 4LO or the 4HI position. Resistances in these ranges will be represented as a Neutral Switch Activation.

TRANSFER CASE MODE SENSOR SIGNAL

The Transfer Case Mode Sensor Signal Input will provide the FDCM feedback about the position of the transfer case. The mode sensor will be a linear analog position sensor with a 1.4K +/- 20% potentiometer and a 1 K +/- 20% wiper resistor that converts the motor shaft position into a multiplexed voltage.

NEUTRAL LAMP

There will be a LED indicator in the Shifter bezel to indicate to the driver that the Transfer Case is in the Neutral gear. FDCM will be capable of driving the LED continuously at 25 mA.

FRONT AND REAR ELECTRONIC LIMITED SLIP DIFFERENTIAL PRESSURE SOLENOID

These outputs will control a Solenoid that regulates the oil pressure inside the Front and Rear Electrical Differential. The oil pressure controls a clutch pack in the front differential that varies the torque transfer across the front or rear axle. The solenoid will be PWM controlled at a 1Khz frequency and with a 0 to 100% duty cycle capability.

TRANSFER CASE BI-DIRECTIONAL MOTOR CONTROL (A AND B)

This output will control a Bi-directional DC motor that controls a clutch pack in the Transfer Case that varies the torque transfer between the front and rear axles.

MODES OF OPERATION

Normal Operation

This mode is achieved by the ignition being switched in the RUN position, which powers up the 5V regulator and generates the appropriate RESET for the microprocessor. This mode also includes any required power-up system checks.

Shut Down Mode

This mode is activated when the ignition switch turned to the off position. The FDCM will perform any required Shut Down tasks prior to turning off the 5V regulator.

Limp-In Mode

This mode is entered when the FDCM has detected an error condition that prevents the system from performing its' required task. The FDCM operation will vary depending from modified operation to total system shut down based on the failure that has occurred.

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