Module Communication Network

The vehicle has two separate 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 [P/LB]) and the International Standards Organization (ISO) 9141 Network via a single wire (circuit 70 [LB/W]). Both networks can be connected to New Generation STAR (NGS) tester at 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 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 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 a termination resistor is lost. This faulted condition is detected and reported to the host by the modules 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.

There are three modules linked to the SCP communication network and seven modules linked to the ISO 9141 communication network.

SCP Communication Network
The Powertrain Control Module (PCM) is on the SCP communication network. The PCM controls the engine for better fuel economy, emissions control and failure mode detection and storage.

The Passive Anti-Theft System (PATS) module is on the SCP communication network. The PATS module contains circuitry to connect the vehicle electrical system, the transceiver module, the vehicle module communications network and the vehicle theft indicator located in the instrument cluster. The PATS module uses a microprocessor to control the system functions. The PATS module microprocessor stores the ignition key codes in non-volatile memory. The PATS module can be diagnosed through the data link connector. The Electronic Automatic Temperature Control (EATC) module is linked to the SCP communication network. The EATC module controls automatic climate functions that maintain the interior at a constant temperature setting.

ISO 9141 Communication Network
The Restraint Control Module (RCM) module is on the ISO 9141 communication network. The RCM controls the deployment of the air bags based on sensor input. The Parking Aid Module (PAM) is on the ISO 9141 communication network. The PAM controls the parking aid system.

The Generic Electronic Module (GEM)/Central Timer Module (CTM) is on the ISO 9141 communication network. The GEM is equipped on vehicles with four-wheel drive or vehicles with power windows. The CTM is equipped on vehicles with two-wheel drive or vehicles without power windows. The GEM controls a variety of systems:
^ 4x4
^ Windshield wipers
^ Courtesy lamps
^ One touch down power windows, etc
^ Warning chimes/lamps

The Remote Anti-theft Personality (RAP) module is on the ISO 9141 communication network. The RAP module controls the keyless remote entry and active anti-theft of the vehicle.

The 4-wheel anti-lock brake control module is on the ISO 9141 communication network. The 4-wheel anti-lock brake control module controls the brake pressure to the four wheels to keep the vehicle under control while braking.

The air suspension system is a computer controlled suspension system. The rear shock absorber contains an integrated air spring. The rear air springs provide automatic load leveling and a ride adjustment with a total span of 50 mm (2 in).

The air suspension control module programming has a time delay compensation for normal suspension travel over rough roads so the air suspension system will not attempt to continuously adjust vehicle ride height.

There is one height sensor mounted in the rear of the vehicle. The height sensors have a total travel range of 80 mm (3 in).

The Driver Seat Module (DSM) is connected on the SCP communication network. The DSM controls the power seat and memory functions.