The body control system consists of the following 2 modules:

The main features of the instrument panel module (IPM) are:

The instrument panel module (IPM) is the gateway between low speed and high speed GMLAN serial data circuits. The purpose of the gateway is to transfer serial data messages from one subnet to another. The IPM shall unpack the signals from frames received from one bus that are to be transmitted across the gateway and repack the signals into frames to be transmitted on the other bus. The IPM shall be responsible for data passing only. The data passed from one bus to the other shall in no way be modified by the IPM gateway function. The IPM receives 3 distinct types of messages on a given bus:

The IPM is the power mode master (PMM). Refer to Power Mode Description and Operation for more information.

Load Management

The power management function is designed to monitor the vehicle electrical load and determine when the battery is potentially in a high discharge condition. This is accomplished by using a high accuracy battery voltage and current reading by a current sensor as an indicator of battery discharge rate. The following 6 levels of load management will execute in the load management control algorithm when there is a high discharge condition:

1. The first action requests a vehicle idle speed increase to the engine control module (ECM) in order to raise alternator output.
2. The second action requests a greater vehicle idle speed increase to the ECM in order to raise alternator output.
3. The third action begins to shed vehicle loads in an attempt to remedy the heavy discharge condition.
4. The fourth action requests another vehicle idle speed increase to the ECM in order to raise further the alternator output.
5. The fifth action begins to shed further vehicle loads in an attempt to remedy the heavy discharge condition.
6. If the above 5 corrective actions fail, the sixth action of power management further sheds loads in a final attempt to remedy the high discharge condition.

Loads subject to reduction include the following:

For more information about load shedding, refer to Load Shed System Description and Operation in Engine Electrical.

Each load management function, either idle boost or load-shed, is discrete. No 2 functions are implemented at the same time. During each load management function, the power mode master (PMM) checks the battery temperature, battery voltage and amp-hour calculations and determines if the PMM should implement a different power management function.

Regulator Voltage Control (RVC)

Regulator voltage control (RVC) will result in the battery being charged at its optimum voltage for improved battery life and state of charge (SOC), fuel economy and lamp life by lowering the system voltage when the SOC is high. The electrical power management (EPM) algorithm in the instrument panel module (IPM) will determine the optimum charging voltage, based on estimates of its SOC and battery electrolyte temperature. Optimum charge voltage is defined as the battery charge voltage that results in maximum battery life, while maintaining energy storage for engine starting, discharge at idle, and parasitic loads. The optimum battery charge voltage will be converted to a percent duty cycle command that will be sent to the ECM via serial data link. The ECM will then place the 128 Hz pulse width modulation (PWM) duty cycle on the L line.

The instrument panel module (IPM) performs multiple body control functions. The IPM can control devices directly connected to its outputs based on input information. The IPM evaluates this information and controls certain body control systems by commanding outputs on or off. The IPM inputs can be:

The IPM is also capable of controlling other vehicle systems that are not directly wired to the IPM, through serial data messages. Some of the functions that the IPM controls or contributes to, are:

The various rear integration module (RIM) inputs and outputs are described in the corresponding functional areas as indicated on the RIM electrical schematics. The RIM functions include the following: