Instrument Cluster: Description

Fig 1: Instrument Cluster

Courtesy of DAIMLERCHRYSLER CORP.

The instrument cluster for this model is an ElectroMechanical Instrument Cluster (EMIC) that is located above the steering column opening in the instrument panel, directly in front of the driver. See Fig 1. The remainder of the EMIC, including the mounts and the electrical connections, are concealed within the instrument panel behind the cluster bezel and beneath the instrument panel top cover for the cluster. The instrument cluster includes analog gauges, meters, indicators, and acoustic signal transmitters.

Fig 2: Instrument Cluster Components

Courtesy of DAIMLERCHRYSLER CORP.

The EMIC module also incorporates a multi-function indicator that consists of a digital Liquid Crystal Display (LCD) unit for displaying odometer/trip odometer information, an electronic digital clock, engine oil level information, automatic transmission gear selector position (PRNDL), and certain diagnostic information. The multi-function indicator also has four push button switches, which provide the vehicle operator with an interface to adjust certain inputs to the instrument cluster and to select from multiple display options. If the vehicle is equipped with the appropriate options, the multi-function indicator also provides an outside ambient temperature indicator display and an Active Service System (ASSYST) engine oil maintenance indicator to display engine oil level and maintenance reminders.

The EMIC gauges and indicators are visible through a dedicated opening in the cluster bezel on the instrument panel and are protected by a clear plastic cluster lens that is secured by eight integral latches to the molded black plastic cluster hood. Four, black plastic multi-function indicator switch push buttons protrude through dedicated holes in a rectangular black plastic switch bezel that is integral to the cluster lens and located near the lower edge of the cluster directly below the multi-function indicator LCD unit. The cluster hood serves as a visor and shields the face of the cluster from ambient light and reflections to reduce glare. The cluster hood has eight integral latches that engage eight integral latch tabs on the cluster rear cover, sandwiching the cluster housing unit between the hood and the rear cover. The cluster hood also has two integral pivot loops molded into its underside that engage two pairs of molded pivot hooks that are integral to the top of the instrument panel base structure. These pivots allow the cluster to be rolled rearward to ease service access to the wire harness connectors at the back of the cluster. See Fig 2.

The rear of the cluster housing and the EMIC electronic circuitry are protected by the molded plastic rear cover. A mounting ear at each upper corner of the rear cover are used to secure the EMIC to the molded plastic instrument panel base unit with two screws. The rear cover includes clearance holes for the two cluster connector receptacles on the cluster electronic circuit board. The connector receptacles on the back of the cluster electronic circuit board connect the EMIC to the vehicle electrical system through two take outs with connectors from the vehicle wire harness. The EMIC rear cover includes a molded mounting tab and a latch feature that secures the Remote Keyless Entry (RKE)/immobilizer module to the back of the cluster. The RKE/immobilizer module is connected to the vehicle electrical system through a separate take out and connector of the vehicle wire harness.

Located between the rear cover and the cluster hood is the cluster housing. The molded plastic cluster housing serves as the carrier for the cluster electronic circuit board and circuitry, the cluster connector receptacles, the gauges, a Light Emitting Diode (LED) for each cluster indicator and general illumination lamp, the multi-function indicator LCD unit, electronic tone generators, the cluster overlay, the gauge pointers, the multi-function indicator switches and the four switch push buttons.

The cluster overlay is a laminated plastic unit. The dark, visible, outer surface of the overlay is marked with all of the gauge dial faces and graduations, but this layer is also translucent. The darkness of this outer layer prevents the cluster from appearing cluttered or busy by concealing the cluster indicators that are not illuminated, while the translucence of this layer allows those indicators and icons that are illuminated to be readily visible. The underlying layer of the overlay is opaque and allows light from the LED for each of the various indicators and illumination lamps behind it to be visible through the outer layer of the overlay only through predetermined cutouts. A rectangular opening in the overlay at the base of the speedometer provides a window through which the illuminated multi-function indicator LCD unit can be viewed.

Several versions of the EMIC module are offered on this model. These versions accommodate all of the variations of optional equipment and regulatory requirements for the various markets in which the vehicle will be offered. The microprocessor-based EMIC utilizes integrated circuitry, Electrically Erasable Programmable Read Only Memory (EEPROM) type memory storage, information carried on the Controller Area Network (CAN) data bus, along with several hard wired analog and multiplexed inputs to monitor systems, sensors and switches throughout the vehicle.

In response to those inputs, the hardware and software of the EMIC allow it to control and integrate many electronic functions and features of the vehicle through both hard wired outputs and the transmission of electronic message outputs to other electronic modules in the vehicle over the CAN data bus. (Refer to ELECTRONIC CONTROL MODULES ).

Besides typical instrument cluster gauge and indicator support, the electronic functions and features that the EMIC supports or controls include the following:

• Active Service System  - In vehicles equipped with the Active Service System (ASSYST) engine oil maintenance indicator option, the EMIC electronic circuit board includes a second dedicated microprocessor. This second microprocessor evaluates various data including time, mileage, and driving conditions to calculate the required engine oil service intervals, and provides both visual and audible alerts to the vehicle operator when certain engine oil maintenance services are required.
• Audible Warnings  - The EMIC electronic circuit board is equipped with an audible tone generator and programming that allows it to provide various audible alerts to the vehicle operator, including buzzing and chime tones. An audible contactless electronic relay is also soldered onto the circuit board to produce audible clicks that is synchronized with turn signal indicator flashing to emulate the sounds of a conventional turn signal or hazard warning flasher. These audible clicks can occur at one of two rates to emulate both normal and bulb-out turn or hazard flasher operation. (Refer to ELECTRICAL/CHIME/BUZZER - DESCRIPTION) .
• Panel Lamps Dimming Control  - The EMIC provides a hard wired 12-volt Pulse-Width Modulated (PWM) output that synchronizes the dimming level of all panel lamps dimmer controlled lamps with that of the cluster general illumination lamps and multi-function indicator.

The EMIC houses four analog gauges and has provisions for up to nineteen indicators. See Fig 3. The EMIC includes the following analog gauges:

1. Coolant Temperature Gauge 
2. Fuel Gauge 
3. Speedometer 
4. Tachometer 

The EMIC includes provisions for the following indicators. See Fig 3:

1. Airbag (SRS) Indicator 
2. Antilock Brake System (ABS) Indicator 
3. Brake Indicator 
4. Brake Wear Indicator 
5. Charging Indicator 
6. Clogged Fuel Filter Indicator 
7. Constant Engine Speed (ADR) Indicator 
8. Coolant Low Indicator 
9. Electronic Stability Program (ESP) Indicator 
10. High Beam Indicator 
11. Low Fuel Indicator 
12. Malfunction Indicator Lamp (MIL) 
13. Multi-Function Indicator (LCD) 
14. Park Brake Indicator 
15. Seatbelt Indicator 
16. Traction Control (ASR) Indicator 
17. Traction Control (ASR) Malfunction Indicator 
18. Turn Signal (Right and Left) Indicators 
19. Washer Fluid Indicator 
20. Wait-To-Start Indicator 
21. Water-In-Fuel Indicator 

Fig 3: Gauges & Indicators

Courtesy of DAIMLERCHRYSLER CORP.

Except for the indications provided within the multi-function indicator LCD unit, each indicator in the EMIC is illuminated by a dedicated LED that is soldered onto the EMIC electronic circuit board. Cluster illumination is accomplished by dimmable LED back lighting, which illuminates the gauges for visibility when the exterior lighting is turned on. The cluster general illumination LED units are also soldered onto the EMIC electronic circuit board. The LED units are not available for service replacement and, if damaged or faulty, the entire EMIC must be replaced.

Hard wired circuitry connects the EMIC to the electrical system of the vehicle. These hard wired circuits are integral to the vehicle wire harnesses, which are routed throughout the vehicle and retained by many different methods. These circuits may be connected to each other, to the vehicle electrical system and to the EMIC through the use of a combination of soldered splices, splice block connectors, and many different types of wire harness terminal connectors and insulators. Refer to the appropriate wiring information. The wiring information includes wiring diagrams, proper wire and connector repair procedures, further details on wire harness routing and retention, as well as pin-out and location views for the various wire harness connectors, splices and grounds.

The EMIC modules for this model are serviced only as complete units. The EMIC module cannot be adjusted or repaired. If a gauge, an LED indicator, the multi-fuction indicator LCD unit, an electronic tone generator, the electronic circuit board, the circuit board hardware, the cluster overlay, the cluster housing, the cluster hood, the cluster lens, or the cluster rear cover are damaged or faulty, the entire EMIC module must be replaced.