Information Bus: Description and Operation
COMMUNICATIONS NETWORKPowertrain Control Module (PCM)
The PCM uses the controller area network (CAN). The PCM controls the engine for better fuel economy, emissions control and failure mode detection storage. The PCM also controls all of the passive anti-theft system (PATS) functions.
Check the CAN circuits between the PCM C175b and the data link connector (DLC) C251. The total resistance values must not be more than 5 ohms. If the resistance is more than 5 ohms, there is an open circuit in the CAN, damage to the DLC C251, damage to the PCM C175b, or a problem in the in-line connector.
Instrument Cluster
The instrument cluster uses both the CAN and the standard corporate protocol (SCP) communications networks. The instrument cluster displays a variety of vehicle system status information.
The instrument cluster shares the CAN termination responsibilities with the anti-lock brake system (ABS) module through the use of a split termination resistor.
The instrument cluster shares the SCP communications network termination responsibilities with the lighting control module (LCM) and the driver door module (DDM).
Check the CAN and SCP communications network circuits between the instrument cluster C220 and the DLC C251. The total resistance values must not be more than 5 ohms. If the resistance is more than 5 ohms, there is an open circuit in the CAN or SCP communications network, damage to the DLC C251, damage to the instrument cluster C220, or a problem in the in-line connector.
Anti-Lock Brake System (ABS) Module
The ABS module uses the CAN for communication with the diagnostic tool and other modules on the CAN. The ABS module controls the brake pressure to the 4 wheels to keep the vehicle under control while braking. The ABS module and the instrument cluster share CAN termination responsibilities with the use of a split termination resistor in each module.
Check the CAN circuits between the ABS module C135 and the DLC C251. The total resistance values must not be more than 5 ohms. If the resistance is more than 5 ohms, there is an open circuit in the CAN, damage to the DLC C251, damage to the ABS module C135, or a problem in the in-line connector.
Fire Suppression Module (FSM)
The FSM (if equipped) is connected to the CAN and the international standards organization (ISO) 9141 communications network. The fire suppression system is designed to help reduce the risk of fire in high speed rear impacts. The fire suppression system deploys chemicals designed to suppress the spread of fire or potentially extinguish a fire, thereby providing more time for occupants to escape from a crashed vehicle.
Check the CAN and ISO 9141 communications network circuits between the FSM C3281a and the DLC C251. The total resistance values must not be more than 5 ohms. If the resistance is more than 5 ohms, there is an open circuit in the CAN or ISO 9141 communications network, damage to the DLC C251, damage to the FSM C3281a, or a problem in the in-line connector.
Lighting Control Module (LCM)
The LCM uses the SCP communications network for communication with the diagnostic tool and other modules on the SCP communications network. The LCM, instrument cluster, and the DDM share the SCP communications network termination responsibilities. The SCP communications bus may remain operational when one of the termination resistors is not present.
The LCM controls the vehicle systems:
- warning chimes
- exterior lighting
- interior lighting
- backlighting
- perimeter alarm (if equipped)
Check the SCP communications network circuits between the LCM C2145a and the DLC C251. The total resistance values must not be more than 5 ohms. If the resistance is more than 5 ohms, there is an open circuit in the SCP communications network, damage to the DLC C251, or damage to the LCM C2145a.
Driver Door Module (DDM)
The DDM uses the SCP communications network. The DDM, instrument cluster, and the LCM share the SCP communications network termination responsibilities. The SCP communications bus may remain operational when one of the termination resistors is not present.
The module controls functions of the power seats, power windows, power locks, and remote keyless entry (RKE). If equipped, both the DDM and LCM communicate to control the perimeter alarm functions.
Check the SCP communications network circuits between the DDM C501a and the DLC C251. The total resistance values must not be more than 5 ohms. If the resistance is more than 5 ohms, there is an open circuit in the SCP communications network, damage to the DLC C251, or damage to the DDM C501a.
Air Suspension Module
The air suspension module uses the SCP communications network. The air suspension module controls the rear ride height.
Check the SCP communications network circuits between the air suspension module C2131b and the DLC C251. The total resistance values must not be more than 5 ohms. If the resistance is more than 5 ohms, there is an open circuit in the SCP communications network, damage to the DLC C251, or damage to the air suspension module C2131b.
Electronic Automatic Temperature Control (EATC) Module
The EATC module (if equipped) uses the SCP communications network for communication with the diagnostic tool and other modules on the SCP communications network. The EATC module controls the automatic climate functions that maintain the vehicle interior temperature at a constant setting.
Check the SCP communications network circuits between the EATC module C228a and the DLC C251. The total resistance values must not be more than 5 ohms. If the resistance is more than 5 ohms, there is an open circuit in the SCP communications network, damage to the DLC C251, or damage to the EATC module C228a.
Restraint Control Module (RCM)
The RCM uses the international standards organization ISO 9141 communications network. The RCM controls the deployment of the air bags based on sensor input.
Check the ISO 9141 communications network circuit between the RCM C310a and the DLC C251. The total resistance values must not be more than 5 ohms. If the resistance is more than 5 ohms, there is an open circuit in the ISO 9141 communications network, damage to the DLC C251, or damage to the RCM C310a.
Variable Assist Power Steering (VAPS) Module
The VAPS module (if equipped) uses the SCP communications network for communication with the diagnostic tool and other modules on the SCP communications network. The VAPS module controls the level of power steering assistance available to the driver based on vehicle speed.
Check the SCP communications network circuits between the VAPS module C2231a and the DLC C251. The total resistance values must not be more than 5 ohms. If the resistance is more than 5 ohms, there is an open circuit in the SCP communications network, damage to the DLC C251, or damage to the VAPS module C2231a.
Overhead Console
The overhead console uses the SCP communications network for communication with the diagnostic tool and other modules on the SCP communications network. The overhead console includes a compass display and moonroof controls (if equipped).
Check the SCP communications network circuits between the overhead console C9013a and the DLC C251. The total resistance values must not be more than 5 ohms. If the resistance is more than 5 ohms, there is an open circuit in the SCP communications network, damage to the DLC C251, or damage to the overhead console C9013a.