Instrument Cluster: Operation: Notes

The Electromechanical Instrument Cluster (EMIC) is designed to allow the vehicle operator to monitor the conditions of many of the vehicle components and operating systems. The gauges and indicators in the EMIC provide valuable information about the various standard and optional powertrains, fuel and emissions systems, cooling systems, lighting systems, safety systems and many other convenience items.

The EMIC is installed in the instrument panel so that all of these monitors can be easily viewed by the vehicle operator when driving, while still allowing relative ease of access for service. The microprocessor-based EMIC hardware and software uses various inputs to control the gauges and indicators visible on the face of the cluster. Some of these inputs are hard wired, but most are in the form of electronic messages that are transmitted by other electronic modules over the Programmable Communications Interface (PCI) data bus network.

The EMIC microprocessor smooths the input data using algorithms to provide gauge readings that are accurate, stable and responsive to operating conditions. These algorithms are designed to provide gauge readings during normal operation that are consistent with customer expectations. However, when abnormal conditions exist, such as high coolant temperature, the algorithm can drive the gauge pointer to an extreme position and the microprocessor turns on the Check Gauges indicator and sends an electronic chime request message to the Body Control Module (BCM) over the PCI data bus to provide distinct visual and audible indications of a problem to the vehicle operator.

The EMIC circuitry operates on battery current received through fused B(+) fuses in the Power Distribution Center (PDC) and the Junction Block (JB) on a non-switched fused B(+) circuit, and on battery current received through a fused ignition switch output (run-start) fuse in the JB on a fused ignition switch output (run-start) circuit. This arrangement allows the EMIC to provide some features regardless of the ignition switch position, while other features will operate only with the ignition switch in the On or Start positions. The EMIC circuitry is grounded through two separate ground circuits of the instrument panel wire harness. These ground circuits receive a path to ground through take outs of the instrument panel wire harness with eyelet terminal connectors that are secured by a nut to a ground stud located on the floor panel transmission tunnel beneath the center floor console, just forward of the Airbag Control Module (ACM).

The EMIC also has a self-diagnostic actuator test capability, which will test each of the PCI bus message-controlled functions of the cluster by lighting the appropriate indicators (except the airbag indicator), sweeping the gauge needles across the gauge faces from their minimum to their maximum readings, and stepping the odometer display sequentially from all zeros through all nines. The self-diagnostic actuator test can be initialized manually or by using a DRBIII(R) scan tool. Refer to the appropriate diagnostic information. See the owner's manual in the vehicle glove box for more information on the features, use and operation of the EMIC.