Operation

OPERATION

The ElectroMechanical Instrument Cluster (EMIC) in this vehicle is sometimes referred to as the Cab Compartment Node/CCN or KOMBI. The following information deals primarily with the instrument cluster functions of this unit. Additional details of other electronic functions of this unit may be found within the service information for the system or component that the EMIC controls. For example: Additional details of the audible warning functions of the EMIC are found within the Chime/Buzzer service information.

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 Controller Area Network (CAN) data bus network. Operation.

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, the algorithm can drive the gauge pointer to an extreme position and the microprocessor can sound a chime through the on-board audible tone generator to provide distinct visual and audible indications of a problem to the vehicle operator. The EMIC may also produce audible warnings for other electronic modules in the vehicle based upon electronic tone request messages received over the CAN data bus. Each audible warning is intended to provide the vehicle operator with an audible alert to supplement a visual indication.

The EMIC circuitry operates on battery current received through a fused B(+) fuse on a non-switched fused B(+) circuit, and monitors the electronic ignition switch status messages received from the Electronic Ignition Switch (EIS) (also known as the Electronic Ignition Switch/Central Gateway/EIS/CGW or EZS) over the CAN data bus. 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 a ground circuit and take out of the vehicle wire harness with an eyelet terminal connector that is secured to a stud by a nut at a ground location on the vehicle sheet metal structure.

Proper diagnosis of the EMIC, the CAN data bus or the electronic message inputs to and outputs from the EMIC, as well as the retrieval or erasure of a Diagnostic Trouble Code (DTC) requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.

GAUGES

All gauges receive battery current through the EMIC circuitry only when the instrument cluster detects the ignition switch is in the ON position. With the ignition switch in the OFF position, battery current is not supplied to any gauges, and the EMIC circuitry is programmed to move all of the gauge needles back to the low end of their respective scales. Therefore, the gauges do not accurately indicate any vehicle condition unless the ignition switch is in the ON position.

Each of the EMIC gauges contains an electronically controlled stepper motor unit. The EMIC circuitry completely controls the activation and deactivation of these stepper motors to position each gauge needle in the appropriate position based upon cluster programming and electronic messages received over the CAN data bus.

Proper diagnosis of the gauges, the CAN data bus and the electronic message inputs to the EMIC that control each gauge requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information. Specific operation details for each gauge may be found elsewhere in this service information.

DISPLAYS

A single Liquid Crystal Display (LCD) unit (without steering wheel switches) or two Organic Light Emitting Diode (OLED) display units (with steering wheel switches) are soldered to the EMIC electronic circuit board. The LCD unit and the lower of the two OLED units are fixed segment displays, while the upper OLED display unit is a reconfigurable dot matrix display. With the ignition switch in the OFF or ACCESSORY positions, the fixed segment display is activated and the total odometer information is displayed when either front door is opened (Rental Car mode), and is deactivated after both front doors are closed or after five minutes, whichever occurs first. Otherwise, all display units are active when the ignition switch is in the ON or START positions, and inactive when the ignition switch is in the OFF or ACCESSORY positions.

The illumination intensity of the display units is controlled by the EMIC circuitry based upon inputs from the + (plus) and - (minus) push buttons on the right side of the instrument cluster and electronic messages received over the CAN data bus from the rotary light switch on the instrument panel indicating the exterior lighting is turned ON or, on vehicles equipped with the optional automatic lighting, by electronic messages provided to the EMIC by the rotary lighting switch and the rain/light sensor. The displays are illuminated at full intensity while the ignition switch is in the ON position and the exterior lighting is turned OFF and cannot be adjusted. The illumination intensity of the EMIC displays is synchronized with that of other display units in the vehicle by broadcasting electronic dimming level messages as inputs to all electronic modules in the vehicle over the CAN data bus.

The fixed segment display units have several display capabilities including clock, gear selector indication (PRNDL) and outside temperature. The reconfigurable dot matrix OLED unit displays numerous warning or reminder textual messages, the customer programmable features interface and various diagnostic information when certain fault conditions exist. The push buttons on the instrument cluster and, on vehicles so equipped, the steering wheel are used to control many of the display modes for the display units.

Proper diagnosis of the displays, the CAN data bus and the electronic message inputs to the EMIC that control each display requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information. Specific operation details for each display may be found elsewhere in this service information.

INDICATORS

Indicators are located in various positions within the EMIC and are all connected to the EMIC electronic circuit board. Some indicators operate based upon hard wired inputs to the EMIC, but most are controlled by CAN data bus messages from other electronic modules in the vehicle. Some are controlled by a combination of hard wired inputs, electronic messaging and EMIC programming. If the EMIC loses CAN data bus communication, the EMIC circuitry will automatically turn ON the Malfunction Indicator Lamp (MIL) until CAN data bus communication is restored.

The various EMIC indicators are controlled by different strategies; some receive battery feed from the EMIC circuitry and have a switched ground, while others are grounded through the EMIC circuitry and have a switched battery feed. However, all indicators are completely controlled by the EMIC microprocessor based upon various hard wired and electronic message inputs. Except for the indications provided by the multi-function indicator display units, all indicators are illuminated at a fixed intensity, which is not affected by the selected illumination intensity of the EMIC general illumination lamps.

The hard wired indicator inputs may be diagnosed using conventional diagnostic methods. However, proper testing of the EMIC circuitry and the CAN bus message controlled indicators requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information. Specific details of the operation for each indicator may be found elsewhere in this service information.

CLUSTER ILLUMINATION

The EMIC has several general illumination lamps that are illuminated when the exterior lighting is turned ON. The illumination intensity of these lamps is adjusted by inputs from the + (plus) and - (minus) push buttons on the right side of the instrument cluster and electronic messages received over the CAN data bus from the rotary light switch on the instrument panel indicating the exterior lighting is turned ON or, on vehicles equipped with the optional automatic lighting, by electronic messages provided to the EMIC by the rotary lighting switch and the rain/light sensor. When the ignition switch is in the ON position and the exterior lighting is turned OFF, the EMIC is illuminated at maximum brightness and cannot be adjusted. When the exterior lighting is turned ON, depressing the plus push button brightens the EMIC lighting, and depressing the minus push button dims the EMIC lighting. The illumination intensity of the EMIC is synchronized with that of other display units in the vehicle by broadcasting electronic dimming level messages as inputs to all electronic modules in the vehicle over the CAN data bus.

Proper diagnosis of the EMIC lighting, the CAN data bus and the electronic message inputs to the EMIC that control the EMIC lighting requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.