Spicer TPCS Troubleshooting Guide - Manual (Page 42)

39
Service Codes
Group: 7P! (Codes 31, 32)
Type: Low Air Supply
Air Pressure Check
The Tire Pressure Control 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
Group 7P! displays if the system air pressure supply is too
low to perform a valid tire pressure check.
This may occur because the pressure switch will not close
(inadequate air supply, code 32) or because the pressure
switch or its wiring is shorted, allowing the actual supply
pressure to be lower than anticipated by the system.
Note: To assure a nominal compressor output, code 32 will
not be set unless the pressure switch does not close for
a preset period while the vehicle is being driven at a
speed of over 20 mph.
The components that can cause the pressure switch to remain
open include:
• Air dryer needs service.
• Pressure switch unplugged or damaged wire
harness.
• Faulty pressure switch.
• Faulty compressor.
• Open or broken line from supply tank to Pneumatic
Control Unit.
• Crimped or plugged line from supply tank to Pneu-
matic Control Unit.
• Faulty Electronic Control Unit.
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 7P!
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 Pressure switch won’t
close (32) - Compressor governor cut-out set too low.
- Air dryer needs service.
- Pressure switch unplugged.
- Open or broken line from supply tank to Pneumatic Control Unit.
- Crimped or plugged line from supply tank to Pneumatic Control Unit.
- Faulty pressure switch.
- Faulty compressor.
Supply Tank pressure too
low (32) - Governor cut-in too low.
- Faulty compressor.
- Leaking lines.
Pressure switch failed
closed (31) - Wiring to pressure switch shorted together.
- Faulty pressure switch.