Principles and 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 and data bus minus, (Circuit 915); and the International Standards Organization (ISO) 9141 network, which is a single wire network (Circuit 70 [/WH]). The diagnostic tool 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 SCP communications 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 to modules on the ISO 9141 communication network, the diagnostic tool must ask for all information; the modules cannot initiate communication.

The ISO 9141 communications network will not function if the wire is shorted to ground or battery voltage. Also, if one of the modules on the ISO 9141 communications 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 vehicle 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

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 wheel spin 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 module also controls the Advance Trac(R) System. Advance Trac(R) constantly monitors the vehicle motion relative to the driver's intended course. When there is a discrepancy between the driver's input and the vehicle motion, Advance Trac(R) changes the force at each wheel to help control the vehicle.

The left power sliding door module and right power sliding door module 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 the sensors in the rear bumper that detect close objects when the vehicle is in REVERSE

The Remote Keyless Entry (RKE) is connected to the SCP communication network. The RKE 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 to 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 to 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, interior electronic mirror, and interior lamps

The Next Generation Speed Control (NGSC) servo is connected to 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 to the SCP communication network. The PCM controls the engine performance, electronic ignition, emission controls and on-board diagnostics. The Passive Anti-Theft System (PATS) is integrated into the PCM. The PCM controls the PATS system functions as well as illumination of the anti-theft indicator. The illumination command is sent from the PCM through the SCP communications network to the instrument cluster, which in turn supplies power to the anti-theft indicator. The PCM stores the ignition key codes and controls engine disable.