CENTRAL TIRE INFLATION SYSTEM (CTIS) OPERATION

TM 9-2320-386-24-1-1

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CENTRAL TIRE INFLATION SYSTEM (CTIS) OPERATION

The CTIS allows the operator to manually select a tire pressure suitable to the terrain being traversed.

The system incorporates an Electronic Control Unit (ECU) and air regulating system which provides and

maintains the correct air pressure to all tires at the same time. The ECU controls the manifold which

automatically directs compressed air to inflate the tires or signals the deflation port to deflate the tires

according to the operator-selected terrain setting. The ECU monitors and regulates air system pressure in

30-minute intervals and compensates for thermal tire pressure changes as recommended by the tire

manufacturer.

The CTIS is activated and deactivated with an ON/OFF button on the ECU. In the event the unit is not

deactivated prior to engine shutdown, it will automatically activate when the engine is started again.

Terrain switches on the ECU are pressed by the operator for the terrain conditions which are identified

as emergency, sand/mud/snow, cross-country, and highway. Once the terrain switch has been pressed for

desired pressure setting, the air system inflates and maintains all tires to the appropriate tire pressure

corresponding to a recommended vehicle speed. Provided operator does not experience overspeed

conditions, no additional operator inputs are required once presets have been selected.

The air regulating system consists of a controller overspeed signal generator, power manifold, and wheel

valves. If the operator exceeds the recommended vehicle speed in either emergency, sand/mud/snow, or

cross country modes, an overspeed warning will activate, (flashing max speed display) alerting the operator

of the overspeed condition and to decrease vehicle speed or select a higher tire pressure on the ECU. In the

event the operator fails to slow down or select a higher tire pressure in approximately one minute, the

system will automatically increase air pressure to the tires to the next higher tire pressure setting.

In the event of one or more small air leaks anywhere in the system, such as from a tire puncture or leak

at a connecting line, pressure can be maintained by pressing a terrain switch on the control panel. When

doing so the initial test pressure sequence begins. If the air feeder lines cannot hold at least 6 psi (41 kPa)

the controller display will read FLAT in the upper right corner, indicating to the vehicle operator that a

large air leak, such as a damaged/disconnected air line or a flat tire, exists. When FLAT is indicated, the

vehicle operator may elect to call for assistance, or try to drive to a repair center using the vehicle's run flat

mode.

Should a particular tire or connecting line experience catastrophic failure or a leak which exceeds the

capacity of the compressor, the CTIS may be turned off allowing the wheel valves to keep each tire

individually isolated. Additionally, the damaged portion will remain isolated, as a safety measure, until it

is repaired. A priority pressure switch in the manifold monitors the pressure in the air reservoirs and

isolates the CTIS if this pressure drops below 75 psi (517 kPa). Minimum requirement for the operation of

priority systems (brakes, power steering assist, horn) is less than 75 psi (517 kPa), so safe operation is

assured. If the CTIS suffers complete failure, the operator accesses a manual wheel valve at each wheel

and inflates each tire from an external air source. If tire pressure falls below 10 psi, CTIS will not

inflate tire. The CTIS should be deactivated during operation in extreme cold, 0 to -65 F (-18 to -54 C).

Extreemly cold temperatures can cause air seals located at each wheel to fail.

COOLING SYSTEM OPERATION

The engine has a pressurized cooling system with a shunt line. The system can safely operate at a

temperature higher than the normal boiling point of water, which prevents cavitation in the water pump.

ESP vehicles have a 10-plate transmission oil cooler located in the radiator outlet tank and an auxiliary oil

cooler in front of the radiator. The oil coolers are designed to keep the automatic transmission running at a safe

operating temperature.

Major components of the cooling system are the radiator, charged air cooler, water pump, surge tank,

water thermostat regulator, fan, and fan actuator.

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