Information Bus: Description and Operation

Vehicles Without Compressed Natural Gas (CNG):

Vehicles With Compressed Natural Gas (CNG):

The Powertrain Control Module (PCM) governs all operations in connection with the engine. The PCM is linked to the Data Link Connector (DLC) through the diagnostic data bus (SCP). Data stored in the PCM can be read through the DLC using the scan tool.

The Passive Anti-theft System (PATS) module is integrated in the PCM. The PATS module contains circuits connecting the vehicle electrical system, the transceiver module, the vehicle module communications network and the vehicle theft indicator. A microprocessor controls the system functions and stores the ignition key codes in a non-volatile memory. The PATS module can be diagnosed through the DLC. For additional information, refer to Antitheft and Alarm Systems.

The Alternative Fuel Control Module (AFCM) has separate injector drivers to run the injectors at the higher operating pressure of natural gas. The AFCM does not carry out any calculations for this function, calibration for the injectors is maintained within the PCM.

The airbag module controls driver and passenger airbag and the pyrotechnical seat belt tensioners. The airbag module is connected to the DLC through the diagnostic data bus (ISO9141).

The DLC serves as an interface between the modules and the diagnostic tester. This electrical connector is connected to all modules capable of diagnosis through the diagnostic data bus (SCP or ISO9141).

The Anti-lock Brake System (ABS) module controls the anti-lock braking functions through the brake circuits and is connected to the DLC through the diagnostic data bus (ISO9141). The ABS module is also connected to the SCP for communicating with the PCM.

The SCP consists of two lines, the 4-RA1 (GY/VT) and the 5-RA1 (BU/WH), along which communication with the diagnostic tester still takes place, even if one of the two lines is broken, has ground contact or a short-circuit to a battery voltage. Should one of these faults occur, this is stored and can be read out. If both lines are damaged, communication with the modules is no longer possible.

The diagnostic data bus (ISO9141) is a one-strand line 8-DA1 (WH), along which communication is no longer possible if the line is broken, has ground contact or a short-circuit to a battery voltage.