Spicer TPCS Troubleshooting Guide - Manual (Page 36)

33
Service Codes
Group: 3P! (Code 21)
Type: Vacuum Fault
Code Description
Group 3P! displays when the system is generating a
vacuum at a time when the Electronic Control Unit (ECU) is
not requesting a vacuum. Creation of an unexpected vacuum
is highly unlikely.
The most likely cause of an unexpected vacuum is a
contaminated or faulty Pneumatic Control Unit (PCU).
Verify the problem before replacing the Pneumatic Control
Unit. See the procedure in the 3P! Troubleshooting Tree.
See "Troubleshooting Tips" for general guidelines on system
diagnostics.
System Mode Condition Possible Causes
(Listed in Likely Order of Occurrence)
Inflate Only Inappropriate vacuum
generation
- Faulty or contaminated Pneumatic Control Unit.