Spicer CTIS (Central Tire Inflation System) Troubleshooting Guide - Manual (Page 24)

21
Service Codes
5 Flashing Lights or DDM – Dashes "--" (Codes 26, 27)
Type: Low Pressure
Air Pressure Check
Note that the Central Tire Inflation System is not continuously
pressurized; pressure checks occur on a periodic basis. Dur-
ing tire pressure checks, the system delivers compressed air
to each channel for approximately two seconds while moni-
toring the pressure in that channel.
Code Description
A “Low Pressure” code indicates an extreme low pressure
reading. The most likely cause is an open line which would
have a clearly audible leak during a pressure check. A second-
ary cause could be a faulty air delivery system (i.e. Pneumatic
Control Unit [PCU]Low Pressure (Codes 26, 27) electrically or
pneumatically disconnected).
Other components that can cause a Low Pressure code are:
• Electrically or pneumatically disconnected PCU
• Faulty PCU
• Restricted line between the supply tank and PCU
• Faulty PCU sensor
• Open line from PCU to Quick Release Valve
• Open line from Quick Release Valve to Wheel Valve
To correctly diagnose the faulty component, connect the Diag-
nostic Tool (see "Diagnostics" for test equipment and descrip-
tions) and follow the procedure in the Low Pressure
troubleshooting tree.
See “Troubleshooting Tips” for general guidelines on system
diagnostics.
System Mode Condition Possible Causes (listed in order of likely occurrence)
System waits to
check pressures Faulty pneumatic system,
or extremely low pressure
reading • Open line between PCU and wheel valve
• Significant hub air seal leakage
• Open solenoid (PCU electrically or pneumatically disconnected)
• Crimped or plugged line between supply tank and PCU
• Faulty PCU sensor (ex. frozen water contamination)
• PCU failure, supply or control off
• Pressure switch failure, shorted closed
• Faulty ECU