Spicer TPCS Troubleshooting Guide - Manual (Page 6)

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General Information
Wheel Valve
All axles use a Wheel Valve (WV) at each end. Dual wheels are
typically connected through one WV to provide tire pressure
balance, although individual wheel valves for each tire may be
installed. When the system is idle, the wheel valve isolates the
tire(s), ensuring fail-safe operation. A standard valve stem is
included on the WV for manual inflation / deflation / pressure
checking.
Electronic Control Unit (ECU)
The Electronic Control Unit (ECU) is the control center for the
entire Tire Pressure Control System. The ECU receives com-
mands from the driver through the Driver Display Module
(DDM) or Operator Control Panel (OCP) and transmits and
monitors appropriate signals throughout the system.
Driver Interface
Options are available for the TPCS driver interface. The Driver
Display Module (DDM) includes two rocker switches and a
multi-function display. The Operator Control Panel (OCP) uses
a six-button keypad and graphic display.
Pneumatic Control Unit (PCU)
The Pneumatic Control Unit (PCU) is a solenoid controlled
manifold that controls the air system. It also contains the
Pressure Sensor (transducer) which reads tire pressures.
Vehicle Speed
Speed is read from the vehicle data link or a separate speed
sensor.
Pressure Switch
The Pressure Switch (PS) acts as an electronic brake priority
switch. It prevents the Tire Pressure Control System from
using air from the supply tank until the brake system is fully
charged. The PS also ensures that enough pressure exists for
the system to operate properly.
Air Lines
The Tire Pressure Control System uses a dedicated pneumatic
system plumbed from the vehicle’s existing supply tank.
Wiring
A wiring harness (Dana or OEM supplied) provides for electri-
cal signals between appropriate components.