Allison Transmission Motorhome Series Operator's Manual page 86

PC Personal Computer—Needed to run a version of Allison DOC™
diagnostic tool.
PD Powered Downshift—A downshift forced by applying brakes with
the throttle applied. Allison Transmission does not recommend
this procedure.
PDA Personal Digital Assistant—Used to run a version of Allison
DOC™ diagnostic tool.
PT Part Throttle
PTO Power Takeoff
RFI Radio Frequency Interference
ST Step Thru—A downshift forced by applying WOT, just prior to a
CT downshift.
TCM Transmission Control Module—(also commonly referred to as
the "computer" for Allison 4
TPS Throttle Position Sensor—Potentiometer for signaling the
position of the engine fuel control lever.
WOT Wide Open Throttle
WTEC III World Transmission Electronic Controls, Third Generation
th
Generation Controls)
85