Communications Network

COMMUNICATIONS NETWORK

Vehicle Security Module
The vehicle security module is on the universal asynchronous receiver transmitter (UART) based protocol (UBP) communication network. The vehicle security module controls the keyless entry functions for the vehicle.

Driver Seat Module (DSM)
The DSM is on the UBP communication network. The DSM controls the positioning and programming of the driver seat and memory pedals.

Restraint Control Module (RCM)
The RCM is on the international standards organization (ISO) 9141 network. The RCM controls the deployment of the air bags based on sensor input.

Tire Pressure Monitoring System Module
The tire pressure monitoring system module is on the controller area network (CAN). The tire pressure monitoring system module uses one sensor mounted in each tire to sense low tire pressure. When low tire pressure is sensed the module will send a warning to the driver.

Anti-Lock Brake System (ABS) Module
The ABS Module is on the CAN. The ABS module controls the brake pressure to the four wheels to keep the vehicle under control while braking. The ABS module also controls the stability assist and traction control systems (if equipped).

Parking Aid Module
The parking aid module is connected to the ISO 9141 communication network. The module controls sensors in the rear bumper that detect close objects when the vehicle is in reverse.

Powertrain Control Module (PCM)
The PCM is on the CAN and uses this network to communicate with the diagnostic tool. The PCM utilizes an internal termination resistor for normal interface with the CAN. Damage or loss of this termination resistor will result in intermittent operation and or failure of the entire CAN. The PCM controls the engine for better fuel economy, emissions control, failure mode detection and storage, all passive anti-theft system (PATS) functions, as well as all four wheel drive and speed control functions.

Instrument Cluster
The instrument cluster is on both the CAN and the UBP communication networks. The instrument cluster uses the CAN for communication with the diagnostic tool. The UBP network is used by the instrument cluster for communication with other modules on the UBP network. The instrument cluster also passes some information from the CAN modules to modules on the UBP network for inter-module communication. It is an analog face cluster with a digital odometer. The instrument cluster displays a variety of information.

Electronic Automatic Temperature Control (EATC) Module
The EATC module is on the CAN communication network. The EATC module controls automatic climate functions that maintain the vehicle interior temperature at a constant setting.

PRINCIPLES OF OPERATION

The vehicle has three module communication networks:
- controller area network (CAN)
- universal asynchronous receiver transmitter (UART) based protocol (UBP)
- international standards organization (ISO) 9141

The CAN has an unshielded twisted pair cable, data bus plus, circuit 3126 (TN/YE) and data bus minus, circuit 3125 (RD/YE). The UBP communications network uses a single wire network circuit 693 (OG), as does the ISO 9141 communications network, which is a single wire network, circuit 70 (LB/WH). All three networks are connected to the data link connector (DLC). This makes diagnosis and testing of these systems easier by allowing one diagnostic tool to be able to diagnose and control any module on the three networks from one connector. The DLC can be found just above the parking brake release handle.

The CAN permits inter-module communication between the DLC, PCM, instrument cluster EATC module, tire pressure monitoring system module, and the ABS modules. When the diagnostic tool communicates to modules on the CAN, the diagnostic tool must request all information or initiate module commands.

The CAN will not function if the wire is shorted to ground or battery voltage. Also, if one of the modules on the CAN loses power or shorts internally, communications to that module will fail. Both the PCM and the instrument cluster have internal termination resistors required for correct network communications operation.

The UBP network allows inter-module communication. The UBP communications network will not function if the wire is shorted to ground or voltage. If one of the modules on the UBP communications network loses power or shorts internally, communications to that module will fail.

The ISO 9141 communications network does not permit inter-module communication. When the diagnostic tool communicates to modules on the ISO 9141 communication network, the diagnostic tool must ask for all information; the modules cannot initiate communications.

The ISO 9141 communications network will not function if the wire is shorted to ground or voltage. Also, if one of the modules on the ISO 9141 communications network loses power or shorts internally, communications to that module will fail.