Spicer CTIS (Central Tire Inflation System) Troubleshooting Guide - Manual (Page 58)

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Service Codes
No Indication (Codes 61, 62, 64, 65)
Type: Wheel Valve Shut Off
Air Pressure Check
The Central Tire Inflation System is not continuously
pressurized; pressure checks occur on a periodic basis.
During tire pressure checks, the system delivers compressed
air to each channel for approximately two seconds while
monitoring the pressure in that channel.
Code Description
The “Wheel Valve Shut Off” code indicates that the system is
unable to confirm that tires on a given channel are able to sus-
tain the target pressure when the channel is depressurized.
After any change of pressure on a given channel, the Central
Tire Inflation System will return to that channel to confirm, or
"double-check" the new pressure before returning to the peri-
odic check interval. If the pressure is not the same, or more
than the last reading, the system will inflate again, and then
reconfirm that channel. After 7 - 10 confirmation attempts, the
system will log a code, and complete operations on the other
channel. The system will classify the loss of air due to wheel
valve closure as minor (codes 61 and 62 on front and rear) or
major (codes 64 and 65 on front and rear respectively).
Note: Leaks from the tire(s) may be noted after the truck has
been idle overnight, as the tire(s) lose(s) air when the
truck is off and the system inoperative. By observing
the time required to achieve normal tire pressures after
starting the vehicle, many tire punctures can be
identified well before the tire incurs non-repairable
damage.
A confirmation failure can be caused by:
• Damaged or leaking tire(s).
• Leaking air line between the wheel valve and tire.
• Air passage restriction between the Pneumatic Con-
trol Unit (PCU) and the wheel valve.
• Wheel valve contamination or failure.
To identify the root cause of the problem, connect the
diagnostic tool (see Diagnostics Section for test equipment
and descriptions) and follow the procedure in the Tire Leak
(code 41) Troubleshooting Tree.
See "Troubleshooting Tips" for general guidelines on system
diagnostics.
System Mode Condition Possible Causes (listed in order of likely occurrence)
Normal Operation Loss of pressure during
shut off • Wheel valve shut off failure
• Air passage restriction