Instrumentation Control Unit
The following information describes the instrumentation control unit (ICU3S) panel, used with compressed natural gas (CNG) engines. The instrument panel is shown in Fig..
Note: This instrument panel is shown with a standard U.S. speedometer, which shows miles per hour (mph) more prominently than kilometers per hour (km/h). Instruments and controls, and their locations, may vary from those shown.
The ICU3S instrument cluster receives information from the datalink and sensors installed on the vehicle, and sends that information to electronic gauges.
There can be up to eight gauges on the driver's instrument panel (six electronic and two mechanical). Only the air gauges operate mechanically.
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Transmission Temperature Gauge
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Coolant Temperature Gauge
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Engine Oil Pressure Gauge
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Dash Driver Display Screen
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Fuel Level Gauge
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Primary Air Pressure Gauge
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Mode/Reset Switch
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Secondary Air Pressure Gauge
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Speedometer
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Tachometer
Fig. 1, Gauge Layout (typical, U.S.), EPA10 and Newer Engines
Dash Message Center
The dash message center houses all of the standard and optional warning and indicator lights. Warning messages and diagnostic fault codes will appear in the driver display screen.
Ignition Sequence
When the ignition is turned on, all of the electronic gauges complete a full sweep of their dials, the warning and indicator lamps illuminate, and the buzzer sounds for 3 seconds.
Note: The air gauges do not sweep.
Important: If any emergency exit is not closed a buzzer will sound continuously.
The following lamps illuminate during the ignition sequence:
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fasten seat belt warning
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low battery voltage warning
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high coolant temperature warning
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low engine oil pressure warning
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low air pressure warning
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parking brake on indicator
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all engine indicator/warning lamps, including check engine and stop engine
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all ABS indicator/warning lamps, including wheel spin, and tractor ABS (if installed)
Note: While the engine and ABS warning lamps illuminate during the ignition sequence, they are not controlled by the instrument cluster but by their own system electronic control unit (ECU).
When the ignition switch is turned on, the ICU3S performs a self-test, looking for active faults. During the first half of the self-test, all segments of the display illuminate as follows:
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First line (odometer): 888888.8
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Second line (units): TRIP MI KM HOURS
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Third line (voltmeter): 38.8 VOLTS
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Fourth line: SERVICE ENGINE
During the second half of the self-test, the software revision level is displayed.
If there are no active faults, the driver display screen displays the odometer.
If however, the instrument cluster has received active fault codes from other devices, it displays them one after the other until the parking brake is released, or the ignition switch is turned off. Once the parking brake is released, the dash message center displays the odometer again.
Note: If active faults are present, take the vehicle to an authorized Thomas Built Bus service facility as soon as possible.
If the fault requires immediate attention, the stop engine system will activate. In most cases, the check engine lamp will also illuminate.
Some examples include:
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high coolant temperature
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low air pressure
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low coolant level
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low engine oil pressure
Note: The check engine lamp does not illuminate for a low air pressure fault.
The legend SERVICE ENGINE can appear on the driver display screen as an active fault code. If this legend appears, it means the trip miles (or hours) have gone beyond the next required service interval, as set by the vehicle operator.
Important: If the legend SERVICE ENGINE appears on the driver display screen while operating the vehicle, bring the vehicle to an authorized Thomas Built Bus service facility when convenient.
Odometer
The odometer is a seven-digit display with a decimal point, until the vehicle has traveled 999,999.9 miles or kilometers (km). At one million miles (km), the odometer resets itself to 1,000,000, without the decimal point, and can continue up to 9,999,999. The odometer only displays significant figures (no leading zeros).
The odometer is set to display in either miles or kilometers, depending on the primary scale of the speedometer. The legend, either MI or KM, illuminates between the odometer and the volts display when the engine is running or the headlights are turned on.
Mode/Reset Switch
The mode/reset switch, shown in Fig., is located on the right side of the instrument cluster. The mode/reset switch is used to scroll through the displays on the message display screen, and to reset the trip distance and trip hours values to zero.
When the odometer reading is displayed and the parking brake is applied:
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Press the mode/reset switch once and the trip distance will display.
Fig. 2, Mode/Reset Switch
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Press the mode/reset switch a second time and the trip hours (engine hours) will display.
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Press the mode/reset switch a third time and the SELECT screen and the current units, MI or KM, will display.
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Press the mode/reset switch a fourth time to return to the odometer reading.
To reset trip miles and/or trip hours to zero, press the mode/reset switch for 1 second or longer. To toggle between MI (miles) or KM (kilometers), press the mode/reset switch while in the SELECT screen.