Using Shift Selector For Accessing Diagnostics Information; Display Sequence; Diagnostic Code Display And Clearing Procedure; Exiting Diagnostic Mode - PREVOST H3-41 Maintenance Manual

SECTION 07: TRANSMISSION
(historic) is dropped from the list. If all DTCs are
active, the DTC with the lowest priority is
dropped from the list.
An active code is any code that is current in the
TCM decision-making process and has failed the
DTC test(s) associated with that specific
diagnostic algorithm. Historical codes, which are
by definition inactive, are codes that are no
longer failing their algorithm but are retained in
the TCM in order to help the technician analyze
possible causes and provide them direction if the
vehicle is brought in before they are cleared from
the queue.
DTCs can be cleared manually by the operator
or they clear automatically from last (d5) to first
(d1) in the queue after a number of engine
starts, without becoming active again.
6.1.1 Using Shift Selector for Accessing
Diagnostics Information
DTCs can be displayed on the display portion of
the shift selector. A DTC is either active or
historic. An active DTC is a DTC that is current
in the TCM decision-making process. Historic
DTCs are retained in the TCM memory and do
not necessarily affect the TCM decision-making
process.

6.1.2 Display Sequence

Up to five DTCs may be displayed one at a time
from the selector once the diagnostic display
mode has been initiated by the operator. Each
DTC is 5 characters in length. The DTC status
active or inactive is shown below the DTC.
Shows active DTC P0730
The operator presses the MODE button to read
the next DTC in the queue (if any) or requests to
exit diagnostics mode. The diagnostics mode
times out and returns the selector to normal
operating mode after approximately 10 minutes
of operator inactivity.
6.1.3 Diagnostic Code Display and Clearing
Procedure
Diagnostic codes can be read and cleared by
two methods:
o Using an Allison DOC™ diagnostic tool. For
specific instructions on how to use an Allison
22
PA1621 Maintenance Manual All Series | January 2017
DOC™ diagnostic tool, refer to the User
Guide.
o Using the pushbutton shift selector.
To begin the diagnostic process:
1. Bring the vehicle to a stop at a safe location.
2. Apply the parking brake.
To display stored codes:
1. Simultaneously press the
(Downshift) arrow
(Prognostics enabled)
Diagnostic Display Mode. With Prognostics
disabled, press the
(Downshift) arrow buttons twice.
2. Press the MODE button to read the next
code in the queue, if any.
To clear all active stored codes:
While in Diagnostic Mode, clear all active codes
by pressing and holding the MODE button for
approximately three seconds until the MODE
message flashes. Release the MODE button.
The MODE message
illuminated if the active DTC shown in the display
has cleared.
While in Diagnostic Mode, press and hold the
MODE button for 10 seconds to clear both active
codes and inactive codes. The MODE message
flashes a second time indicating all codes are
cleared from the queue.

6.1.4 Exiting Diagnostic Mode

Exit the diagnostic mode by one of the following
methods:
1. Press simultaneously the
(Downshift) arrow buttons at the
same time on the pushbutton shift
selector.
2. Press any range button «D», «N» or «R»
on the pushbutton shift selector.
3. After approximately 10 minutes of
inactivity at the pushbutton shift selector,
the diagnostic mode automatically exits
and returns to normal operating mode.
4. Turn off power to the TCM (shut off the
engine using the ignition key).
(Upshift) and
buttons five times
to access the
(Upshift) and
should not remain
(Upshift) and