Principles of Operation

The vehicle has two module communication networks: the Standard Corporate Protocol (SCP), which is an unshielded twisted pair cable (data bus plus, Circuit 914 [T/O] and data bus minus, Circuit 915 [PK/LB]) and the International Standards Organization (ISO) 9141 communications network, which is a single wire network (Circuit 70 [LB/W]). The New Generation STAR (NGS) Tester can connect to both networks through the Data Link Connector (DLC). This makes diagnosis and testing of these systems easier by allowing one smart tester to be able to diagnose and control any module on the two networks from one connector. The DLC can be found under the instrument panel between the steering column and the radio.

The ISO 9141 communication network does not permit intermodule communication. when NGS Tester communicates to modules on the ISO 9141 communication network, the NGS Tester must ask for all information; the modules cannot initiate 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 battery positive voltage (B+), or if a termination resistor is lost. This faulted condition is detected and reported to the host by the module's network bus interface circuits.

Unlike the SCP, the ISO 9141 communication network will not function if the wire is shorted to ground or battery positive voltage (B+). Also, if one of the modules on the ISO 9141 communication network loses power or shorts internally, communications to that module will fail.

The instrument cluster is connected to the SCP communication network. The instrument cluster displays driver information, including tachometer reading, fuel level, engine coolant level and speed. The message center is included in the high option level cluster and displays door/hatch ajar information, lamp outage and low washer fluid level. Passive anti-theft system is internal to the instrument cluster.

The anti-lock brake control module is connected to the SCP communication network. The module controls the brake pressure to the four wheels to keep the vehicle under control while braking. The module also controls the traction control system. The module controls wheelspin by modulating the engine torque and by applying, then releasing, the appropriate front brake to restore traction when driving on slippery or loose surfaces.

The left power sliding door and right power sliding door modules are connected to the ISO 9141 communication network. The modules control opening and closing of the left and right passenger side doors.

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.

The Remote Keyless Entry (RKE) [Driver Door Module (DDM)] is connected on the SCP communication network. The RKE DDM receives remote transmitter signals and sends the information to the front or rear electronic modules.

The Restraint Control Module (RCM) is connected to the ISO 9141 communication network. The RCM controls the deployment of the air bags based on sensor input.

The Front Electronic Module (FEM) is connected on the SCP communication network. The FEM controls front blower motor, front exterior lamps, interior lamps, front and rear windshield wipers, the driver door lock and the active anti-theft system.

The Rear Electronic Module (REM) is connected on the SCP communication network. The REM controls rear exterior lamps, fuel level information, auxiliary air conditioning, rear defrost, liftgate lock, anti-theft, left and right sliding door locks, passenger door lock, electronic mirror, and interior lamps.

The next generation speed control servo is connected on the SCP communication network. The servo, when activated, controls and maintains vehicle speed by actuating the throttle linkage.

The Powertrain Control Module (PCM) is connected on the SCP communication network. The PCM controls the engine performance, electronic ignition, emission controls and on-board diagnostics.