WORKHORSE CUSTOM CHASSIS
Service Manual
2007 W Series
SECTION
7.2
PAGE
268
Automatic Transmission – Allison
2007 W Series Chassis
© 2006 Workhorse Custom Chassis — All Rights Reserved
WSM082106
DTC P0828
Circuit Description
The transmission adaptive pressure (TAP) up/down
shift system allows the driver to manually shift gears
by using the TAP shift switch located on the automatic
transmission shift lever. Pushing the switch forward will
command an upshift and pushing the switch rearward
will command a downshift. The TAP shift system is
activated when the gear selector is in the manual (M)
position.
DTC P0828 is a type B DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
• DTC P0828 TAP Up and Down Shift Switch Circuit High
Conditions for Running the DTC
• The components are powered and ignition voltage is
greater than 9.0 volts and less than 18 volts.
• The engine, input, speed is greater than 200 RPM and
less than 7,500 RPM for 5 seconds.
• The output speed is greater than 200 RPM.
• Driver shift request is commanded.
Conditions for Setting the DTC
DTC P0828 sets when the transmission control module (TCM)
detects a short to ground condition in the TAP up/down shift
switch circuit for greater than 6 seconds when driver shift request
is commanded.
Action Taken When the DTC Sets
• The TCM illuminates the malfunction indicator lamp
(MIL) during the second consecutive trip in which the
Conditions for Setting the DTC are met.
• DTC P0828 is stored in TCM history.
• The TCM disables driver shift request operations.
Conditions for Clearing the DTC
A scan tool can clear the code from TCM history. The
TCM automatically clears the DTC from TCM history if
the vehicle completes 40 warm-up cycles without failure.
Diagnostic Aids
• Inspect the wiring for poor electrical connections at the
TCM. Inspect for the following conditions:
– A bent terminal
– A backed-out terminal
– A damaged terminal
– Poor terminal tension
– A chafed wire
– A broken wire inside the insulation
• When diagnosing for an intermittent short or open,
massage the wiring harness while watching the test
equipment for a change.
• You may have to drive the vehicle in order to experience
a condition.
Test Description
The numbers below refer to the step numbers on the
