WORKHORSE CUSTOM CHASSIS
Service Manual
2007 W Series
SECTION
7.2
PAGE
150
Automatic Transmission – Allison
2007 W Series Chassis
© 2006 Workhorse Custom Chassis — All Rights Reserved
WSM082106
DTC P0708
Circuit Description
The transmission internal mode switch (IMS) is a sliding
contact switch attached to the selector detent inside
the transmission. The IMS is used by the transmission
control module (TCM) to detect the angular position of
the shift selector shaft. There are 5 internal switches in
the IMS, A, B, C, P and NS. The TCM uses 4 of these
switch inputs to determine the proper gear range that
is selected. The fi fth switch, NS, located in the IMS,
is used as confi rmation that the transmission is in
NEUTRAL before the engine starter is engaged.
DTC P0708 is a type A DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
• DTC P0708 Transmission Range (TR) Sensor Circuit
High
Conditions for Running the DTC
• The components are powered and the ignition voltage is
greater than 9.0 volts and less than 18 volts.
• Engine speed is greater than 200 RPM and less than
7,500 RPM for 5 seconds.
Conditions for Setting the DTC
DTC P0708 sets when the TCM detects an invalid
condition and parity error occurring over consecutive
ignition cycles.
Action Taken When the DTC Sets
While diagnostic response is active, one of the following
conditions can occur:
• The TCM illuminates the malfunction indicator lamp
(MIL).
• The transmission fails to hydraulic default.
• A shift to REVERSE will allow REVERSE range if DTC
P0878 is not active.
• DTC P0708 is stored in TCM history.
• The TCM freezes shift adapts.
• The TCM inhibits torque converter clutch (TCC)
engagement.
Conditions for Clearing the DTC
• A scan tool must be used to clear the code from TCM
history. This DTC does not automatically clear from TCM
history after 40 ignition cycles.
Diagnostic Aids
IMPORTANT:
Due to the TCM logic used to detect and set DTC
Due to the TCM logic used to detect and set DTC
P0708, this code can remain active even after an IMS
P0708, this code can remain active even after an IMS
switch replacement is complete and the ignition has
switch replacement is complete and the ignition has
been cycled. Therefore, always clear all active DTCs
been cycled. Therefore, always clear all active DTCs
from the TCM after servicing the IMS switch.
from the TCM after servicing the IMS switch.
• Inspect the wiring for poor electrical connections at the
TCM and powertrain control module (PCM). Inspect for
the following conditions:
– A bent terminal
– A backed-out terminal
– A damaged terminal
– Poor terminal tension
