Spicer TPCS Troubleshooting Guide - Manual (Page 41)

38
Service Codes
Group: 5P! (Codes 26, 27,
28
)
Low Pressure Reading (Codes 26, 27, 28)
Using the diagnostic tool, check faults to
identify the faulty channel:
Front (26)
Rear (27)
Trailer (28)
Initiate inflate mode for the faulty channel.
Yes
Replace PCU 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.
Refer to Service Manual
Replace ECU and recheck system.
Note: ECUs are not a typical cause of problems. If
an ECU is replaced, the system should be carefully
rechecked to make sure the problem has been
fixed and does not reoccur.
Is there extreme
pressure loss?
Identify cause of air loss,
repair and recheck system.
Refer to Service Manual
Use the diagnostic tool to pressurize
and hold the faulty channel.
Does pressure
drop quickly?
Locate leak (check axle
vents for air leakage also),
repair and recheck system.
Does the
pressure switch
open?
Replace pressure switch
and recheck system.
Refer to Service Manual
Does fault
reoccur?
Complete
Verify that the pressure switch opens
when the supply tank is below 80 psi.
Note: Primary and secondary air brake
gauges do not reflect actual pressure in
the supply tank.
Is there a
restricted line between
the wet tank and
PCU?
After a pressure
check, is the pressure
reading <5 psi?
Replace PCU sensor
and recheck system.
Check harness and PCU for open supply or
control solenoids. See Group 12C! PCU
Solenoids, Codes 54 or 56 for procedure.
No
Yes
No
Yes
Identify cause of air loss,
repair and recheck system.
Refer to Service Manual
No
No
No
No
Yes
Yes
Yes