Spicer CTIS (Central Tire Inflation System) Troubleshooting Guide User Manual
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Service Codes
Deflate T
rend (Code 14)
Deflate Trend (Code 14)
Yes
Using the diagnostic tool, manually
deflate the tires on one channel.
While
deflating, is the
system (relief valve)
pressure within 1 psig
of nominal? *
Continue using diagnostic tool
to deflate the tires to 45 psi.
Use manual pressure gauge
to verify all tires at 45 psi.
Use diagnostic tool to select
Check & Hold.
Pressure
reading < 55
psi?
2-channel
system?
Test should
be repeated for both
channels. Both channels
tested?
Are the tires
deflating?
Use diagnostic tool to
manually deflate the tires on
the other channel.
Fault is not active.
Reverify flowchart
steps and wait for fault
to reoccur.
Check wheel valve filters, replace as
necessary and recheck system.
Will the tires
deflate now?
Vent wheel valve covers
and recheck system.
Repair PCU restriction and
recheck system.
Is the PCU
vent line or relief
valve plugged or
restricted?
Use diagnostic tool to place system
into “pressure check and hold” mode.
Check for upper control line leaks.
Make repairs to faulty components.
Use diagnostic tool to
manually deflate the tires.
Replace PCU relief valve
and recheck system.
Perform continuity check on
front and rear channel
solenoids. See Solenoid
Fault flowchart.
Complete
Yes
Yes
Yes
Yes
No
No
No
No
No
No
Yes
Yes
No
2-channel
system?
Are the tires
deflating?
PCU is contaminated or faulty.
Clean, repair and/or replace
PCU as necessary and recheck
system.
Note: While replacing the PCU,
pay particular attention to
possible air line contamination
(e.g., oil, water, particles) which
may suggest further air system
maintenance needs.
PCU is contaminated or faulty.
Clean, repair and/or replace
PCU as necessary and recheck
system.
Note: While replacing the PCU,
pay particular attention to
possible air line contamination
(e.g., oil, water, particles) which
may suggest further air system
maintenance needs.
* Reference vehicle build
information for nominal
relief valve pressure.
While
deflating, is the
system (relief valve)
pressure within 1
psig of
nominal? *
No
No
No
Yes
Yes
Yes