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 and data bus minus, and the International Standards Organization (ISO) 9141 communications network, which is a single wire network. Both networks can be connected to the diagnostic tool by one connector called the Data Link Connector (DLC). This makes troubleshooting 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 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 SCP 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.

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

The anti-lock brake control module is connected to the SCP communication network. It controls the brake pressure to the four wheels to keep the vehicle under control while braking. The SCP communication network is used for diagnosis and communication between other SCP networked modules.

The Audio Control Module (ACM) is connected to the SCP communication network and also to the Audio Control Protocol (ACP) communication network. The ACM communicates with the compact disc player/changer. Refer to Radio, Stereo, and Compact Disc.

The Remote Keyless Entry Module (RKE) is connected to the SCP communication network. The module controls remote keyless entry. Refer to Locks.

The Dual Automatic Temperature Control (DATC) module is connected to the SCP communication network. The DATC module controls automatic climate functions that maintain the vehicle at a constant temperature setting. Refer to Heating and Air Conditioning.

The instrument cluster (also known as an Instrument Cluster Module (ICM)) is connected to the SCP communication network. The instrument cluster displays information received on the SCP including speedometer, odometer, fuel, and message center warnings. Refer to Instrument Panel, Gauges and Warning Indicators for instrument cluster operation.

The Front Electronic Module (FEM) and rear electronic module (REM) are connected to the SCP communication network. The FEM and REM control interior and exterior lighting, wipers, power windows, fuel pump, deck lid, powerlocks, perimeter alarm and the convertible top. Refer to Multifunction Electronic Control Module (General Module).

The Powertrain Control Module (PCM) is connected to the SCP communication network. The PCM controls the engine performance, electronic ignition, emission controls, speed control, and on board diagnostics. Refer to Computers and Control Systems.

The Restraint Control Module (RCM) is connected to the ISO 9141 communication network. The RCM controls the deployment of the air bags and safety belt pretensioners based on sensor input. Refer to Air Bag Systems.