Computers and Control Systems: Description and Operation
System Input/Output And Control:
SYSTEM DESCRIPTION:
This vehicle uses several electronic components which form an electronic computer network, designed to control various engine and body sub-systems. The heart of the computer network is the Body Computer Module (BCM). The BCM has an internal microprocessor which is the center for communication with all the other components, and controls the on-board diagnostics of the vehicle. All system sensors and switches are monitored by the BCM or one of the five other major components that complete the computer system network. The other five components are the Climate Control Driver Information Center (CCDIC), Diagnostic Energy Reserve Module (DERM) Supplemental Inflatable Restraint (SIR) controller, Powertrain Control Module (PCM), Heating, Ventilation, and Air Conditioning (HVAC) Programmer, and the Instrument Panel Cluster (IPC).
ON-BOARD DIAGNOSTICS SYSTEM OPERATION
This vehicle is equipped with an extensive on-board diagnostic system which is capable of detecting and compensating for faults, alerting the operator of a fault and recording pertinent data during the failure. It is also capable of displaying information about current vehicle performance when a fault occurred.
In order to access and control the self diagnostics features available, additional electronic components are utilized by the service technician. The Electronic Climate Control (ECC) and the Fuel Data Center (FDC) provide displays and keyboard switches.
The display and keyboard information is transmitted over a single wire data circuit which carries the coded data messages back and forth between the different control computers. and the display panels (ECC/FDC). This communications process allows the appropriate computer to transfer any of its available diagnostic information to the appropriate panel for display during service. By depressing appropriate buttons on the ECC, data messages are requested to be displayed on the FDC. the diagnostics mode, the mode indicators on the Electronic Climate Control (ECC) are used to indicate system operating modes. The different modes of operation are indicated by the status indicator either being turned "ON" or turned "OFF".
SELF DIAGNOSTICS
Climate Control Driver Information Center:
The CCDIC is used by the driver to control the air conditioner and heating system, also used to retrieve diagnostic information (i.e. trouble codes, sensor parameters, etc.), or override certain output components. The DERM monitors, detects, and records the SIR system during operation when system components malfunction, stores the malfunction as a trouble code, and maintains a 36 volt loop reserve energy supply to provide deployment energy in the event the vehicle voltage is low or lost during an accident. The PCM controls the fuel and ignition systems to obtain good performance and low exhaust emissions. The IPC is used to display information to the driver such as vehicle speed, engine rpm, and fuel level. The HVAC Programmer receives information from the CCDIC and carries out the commands necessary to obtain the correct interior temperature.
SERIAL DATA
All components in the system are always in continuous communication with each other to provide accurate control over the many sub-systems involved. When one or more of these sub-system circuits exceeds pre-programmed limits a malfunction is indicated by a service engine soon warning lamp, and a backup function may be activated until the malfunction is corrected. The communications line is a single circuit (CKT 800) which is referred to as the data line or serial data line.