Principles of Operation

PRINCIPLES OF OPERATION

The vehicle has 4 module communication networks:
- controller area network (CAN) 6.0L diesel
- international standards organization (ISO) 9141
- standard corporate protocol (SCP)
- universal asynchronous receiver-transmitter (UART)-based protocol (UBP)

The diagnostic tool connects to the communication networks through a data link connector (DLC). The DLC allows a diagnostic tool access to diagnose and test the vehicle systems of any module on the networks.

The CAN communications network is a high speed communication network used for 6.0L diesel powertrain communication. The CAN communication network will remain operational even with the severing of one of the bus wires. Communications will also continue if one of the bus wires is shorted to ground or voltage, or if some but not all termination resistors are lost.

The ISO 9141 communications network does not permit intermodule communication. When the diagnostic tool communicates on the ISO 9141 communication network, the diagnostic tool must request all information or initiate module commands. The ISO 9141 communications network will not function if the wire is shorted to ground or voltage.

The SCP communications network uses a twisted wire pair to provide intermodule and diagnostic tool communications. The SCP network will remain operational even with the severing of one of the bus wires. Communications will also continue if one of the bus wires is shorted to ground or voltage, or if some but not all termination resistors are lost.

The UBP communication network provides intermodule and diagnostic tool communications.The UBP network will not function if the wire is shorted to ground or voltage, or if a termination resistor is lost.

The anti-lock brake system (ABS) module communicates on the ISO 9141 network. The ABS module monitors the wheel speed readings from each anti-lock brake sensor and processes this information to determine an impending wheel lock-up. If a wheel lock-up is detected, the ABS module will modulate the brake pressure to the appropriate brake caliper.

The 4-wheel drive (4WD) control module (if equipped) is on the ISO 9141 communication network. The 4WD control module monitors and regulates the four wheel drive operation for the vehicle.

The restraint control module (RCM) communicates on the ISO 9141 network. The RCM monitors and controls the supplemental restraint system (SRS). The SRS is designed to provide increased crash protection for front seat occupants. The RCM will deploy the vehicle air bags based on sensor input during a crash event.

The message center is connected to the ISO 9141 communication network. The message center computes and displays in metric or English: average fuel economy, distance to empty and compass heading.

The parking aid module is connected to the ISO 9141 communication network. The module monitors sensors mounted in the rear bumper that detect the proximity of objects to the vehicle when the vehicle is in reverse. refer to Collision Avoidance and Parking Assist Systems.

The 5.4L and 6.8L PCM is hardwired to the SCP network. The PCM receives input from sensors and other electronic components (switches, relays). Based on the information received and programmed into its memory, the PCM generates output signals to control various relays, solenoids and actuators.

The 6.0L diesel PCM is hardwired to two communication networks. Diagnostic data is provided through the CAN network to the diagnostic tool. Stand-alone modules exchange information with the PCM through the SCP network. The PCM receives input from sensors and other electronic components (switches, relays). Based on the information received and programmed into its memory, the PCM generates output signals to control various relays, solenoids and actuators.

The auxiliary powertrain control module (APCM) is a diesel-engine option which is connected to the SCP communication network. The APCM provides an operator interface to the drive-by-wire powertrain control system to affect charge protection, rpm control, and manual throttle control.

The passive anti-theft system (PATS) module (if equipped) is connected to the SCP communication network. The PATS module communicates with the PCM to enable engine operation and does not require any activity from the user to deter vehicle theft.

The instrument cluster is connected to the SCP communication network and the UBP communication network. Diagnostic data is supplied through the SCP network to the diagnostic tool. Intermodule communication is provided on the SCP and UBP network (dependent upon vehicle content). The instrument cluster contains a variety of warning lights and gauges that display vehicle specific information. This allows the driver to continually monitor vehicle conditions.

The driver seat (DSM) module (if equipped) is connected to the UBP communication network. The DSM controls the driver power seat. The DSM is programmable and will store seat and pedal position.

The electronic automatic temperature control (EATC) module (if equipped) is connected to the UBP communication network. The EATC module controls the automatic climate functions to maintain the vehicle at a constant temperature setting.

The vehicle security module is on the UBP communication network. The vehicle security module controls a variety of systems:
- remote keyless entry (RKE)/keyless entry
- exterior lamps (RKE flash and panic)
- lock/unlock functions