Spicer TPCS Troubleshooting Guide - Manual (Page 40)

37
Service Codes
Group: 5P! (Codes 26, 27, 28)
Type: Low Pressure Reading
Air Pressure Check
The Tire Pressure Control System is not continuously pres-
surized; 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
Group 5P! indicates an extreme pressure loss on the front
(26), rear (27), or trailer (28) channels. Possible causes are
leaking axle air seals or an open line, which would be clearly
audible during pressure measurements.
Note: In extremely cold conditions, air seals will sometimes
leak, resulting in a code 5P!. This code may clear by
simply driving the vehicle for a few minutes to "warm
up" the seals allowing proper system operation.
Other possible causes of a group 5P! are:
• Open line from Pneumatic Control Unit (PCU) to
channel.
• Restricted line between the supply tank and Pneu-
matic Control Unit.
• Faulty PCU Sensor.
• Faulty PCU.
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
5P! Troubleshooting Tree.
See "Troubleshooting Tips" for general guidelines on system
diagnostics.
System Mode Condition Possible Causes
(Listed in Likely Order of Occurrence)
Pressure Check Only Extreme pressure loss - Leaking axle seals.
- Open line between Pneumatic Control Unit to channel.
- Crimped or plugged line between supply tank and Pneumatic Control Unit.
- Pressure switch failure, shorted closed.
- Pneumatic Control Unit failure, supply or control off.
- Faulty pressure transducer.