Body Control System Description And Operation

The body control system consists of the following 3 modules:
^ The Dash Integration Module (DIM)
^ The Instrument Panel Module (IPM)
^ The Rear Integration Module(RIM)

Each of the 3 body control modules integrate a number of functional systems under the control of a single module. Each module is connected to the Class 2 serial data circuit, many of the control signals are implemented by Class 2 messages.

Dash Integration Module (DIM)
The various DIM input and output circuits are described in the corresponding functional areas as indicated on the DIM electrical schematics.

The DIM functions include the following:
^ A/C refrigerant low temperature sensor signal.
^ Air conditioning orifice solenoid control.
^ Backlight lamps control.
^ Control of headlights and exterior lamps.
^ Control power control.
^ DRL relay control.
^ Flash to pass signal.
^ Headlamps on w/wipers signal.
^ Headlamps switch signal.
^ Horn relay control.
^ Interior lamps incandescent dimming.
^ Power moding control over Class 2 serial data line.
^ Reverse lockout solenoid control.
^ Storage of the clock settings and, sending a message out on the class 2 serial data circuit in response to requests from other modules.
^ Steering wheel controls.

Serial Data Power Mode
On vehicles that have several control modules connected by serial data circuits, one module is the Power Mode Master (PMM). On this vehicle the PMM is the DIM. The PMM receives 4 signals from the ignition switch.

To determine the correct power mode the PMM uses the following circuits:
^ Accessory voltage
^ Run/Crank voltage
^ Ignition 3 voltage
^ Off/Run/Crank voltage

Fail-safe Operation
Since the operation of the vehicle systems depends on the power mode, there is a fail-safe plan in place should the PMM fail to send a power mode message. The fail-safe plan covers those modules using exclusively serial data control of power mode as well as those modules with discrete ignition signal inputs.

Serial Data Messages
The modules that depend exclusively on serial data messages for power modes stay in the state dictated by the last valid PMM message until they can check for the engine run flag status on the serial data circuits. If the PMM fails, the modules monitor the serial data circuit for the engine run flag serial data. If the engine run flag serial data is True, indicating that the engine is running, the modules fail-safe to RUN. In this state the modules and their subsystems can support all operator requirements. If the engine run flag serial data is False, indicating that the engine is not running, the modules fail-safe to OFF-AWAKE. In this state the modules are constantly checking for a change status message on the serial data circuits and can respond to both local inputs and serial data inputs from other modules on the vehicle.

Discrete Ignition Signals
Those modules that have discrete ignition signal inputs also remain in the state dictated by the last valid PMM message received on the serial data circuits. They then check the state of their discrete ignition input to determine the current valid state. If the discrete ignition input is active, battery positive voltage, the modules will fail-safe to the RUN power mode. If the discrete ignition input is not active, open or 0 voltage, the modules will fail-safe to OFF-AWAKE. In this state the modules are constantly checking for a change status message on the serial data circuits and can respond to both local inputs and serial data inputs from other modules on the vehicle.

Dim Wake-up/sleep States
The DIM is able to control or perform all of the DIM functions in the wake-up state. The DIM enters the sleep state when active control or monitoring of system functions has stopped, and the DIM has become idle again. The DIM must detect certain wake-up inputs before entering the wake-up state. The DIM monitors for these inputs during the sleep state, where the DIM is able to detect switch transitions that cause the DIM to wake-up when activated or deactivated. Multiple switch inputs are needed in order to sense both the insertion of the ignition key and the power mode requested. This would allow the DIM to enter a sleep state when the key is IN or OUT of the ignition.

The DIM will enter a wake-up state if any of the following wake-up inputs are detected:
^ Activity on the serial data line.
^ Detection of a battery disconnect and reconnect condition.
^ Headlamps are on.
^ Ignition is turned ON.
^ key-in-ignition switch.
^ Parklamps are on.

The DIM will enter a sleep state when all of the following conditions exist:
^ Ignition switch is OFF.
^ No activity exists on the serial data line.
^ No outputs are commanded.
^ No delay timers are actively counting.
^ No wake-up inputs are present.

It all these conditions are met the DIM will enter a low power or sleep condition. This condition indicates that the DIM, which is the PMM of the vehicle, has sent an OFF-ASLEEP message to the other systems on the serial data line.

Instrument Panel Module (IPM)
The various IPM input and output circuits are described in the corresponding areas as indicated on the IPM electrical schematics.

The IPM functions include the following:
^ Ambient light sensor input and twilight delay input for headlights control.
^ Foglamp switch input.
^ Front HVAC air delivery and temperature controls.
^ Ignition switch headlight control.
^ Interior lamps switch input.
^ IP dimmer switch input.
^ key cylinder lamp control.
^ key-in-ignition switch input from the ignition switch.
^ Rear compartment lid release switch input.
^ Traction control switch input.

Rear Integration Module (RIM)
The various RIM input and output circuits are described in the corresponding functional areas as indicated on the RIM electrical schematics.

The RIM functions include the following:
^ Automatic level control.
^ CIGAR relay control.
^ Fuel door release relay control.
^ Heated seat controls.
^ Heating, Ventilation, And Air Conditioning (HVAC) blower control.
^ Inadvertent power relay control.
^ Park brake relay controls.
^ Rear defogger relay control.
^ Rear foglamp relay control.
^ Retained Accessory Power (RAP) control.
^ Reverse lamp relay control.
^ Trunk ajar switch signal.
^ Trunk release relay control.
^ Various controls for the interior lamps.