Engine Controls - Tests W/Codes - BCM: Operation

A combination of inputs from the major components, sensors and switches, communicate together with the BCM. Various inputs to the BCM combine with program instructions within system memory, providing accurate control over all subsystems involved. When a subsystem circuit exceeds preprogrammed limits, a system malfunction is indicated and certain back-up functions may be provided. The BCM controls subsystems through direct outputs or through data transmitted along the serial data line to one of the other major components. The process of receiving, storing, testing and controlling information is continuous. The data communication also gives the BCM control over the ECM's self-diagnostic capabilities. Between the BCM and the other major components of the computer system, a data line communication process has been incorporated, that allows devices to share information and thereby provides additional control capability.

In order to access and control the BCM self-diagnostic features, 2 electronic components are used, the IPC and the ECCP (or the CRT monitor - optional equipment). See Figs. 1 and 2.

The Toronado/Trofeo "service mode" for diagnostic information incorporates a 20-character Driver Information Center (DIC) display. The DIC display is located on the instrument panel cluster. When a malfunction is sensed by the BCM computer system, one of the driver warning messages is illuminated on the DIC. When the "service mode" is entered, various BCM, ECM or IPC faults can be displayed. In addition to the parameters, fault codes, inputs and outputs, other features such as override commands, snapshot, display VIN and code clearing capabilities can be accessed and displayed when commanded through the CRTM or ECCP.

Certain system malfunctions cause computer controlled diagnostic messages and/or telltales to appear, indicating that service is required. When a subsystem circuit exceeds preprogrammed limits, a system malfunction is indicated and the BCM provides certain back-up functions known as "failsoft." A typical "failsoft" action would be the substitution of a fixed input value when a sensor is detected to be open or shorted.

The CRT monitor or ECC panel becomes the controller by which to enter diagnostics and access BCM self-diagnostics. By pressing or touching the appropriate buttons on the CRT monitor or ECC panel, data messages can be sent to the BCM, requesting specific diagnostic features. This communication process allows BCM to transfer any of its available diagnostic information to the instrument panel's 20 character DIC display during "service mode" operation. When in the override mode of BCM diagnostics, the information is displayed at the ECCP temperature LED display or on the CRT monitor. The following is a list of computer controlled subsystems.

• Alternator/Starter System
• Chime
• Climate Control
• Compass
• Courtesy Lights
• CRT Display
• Cruise Control
• Dimming (Lighting)
• Driver Diagnostics
• ECM Subsystems
• Gauges
• Illuminated Entry
• Instrument Panel Displays
• Phone
• Radio
• Self-Diagnostics System
• Trip Data
• Twilight Sentinel