247
2008 IMPERIAL
CHASSIS INFORMATION — 10
NOTE:
The transmission will not accept a
manually selected gear change to occur
if the gear selected is out of the specified
operating range.
NOTE:
The transmission will not shift into gear
from Neutral if the engine RPM is at or
above 900. The display will flash “66”
indicating the engine RPM is excessive.
Select “N” and lower engine RPM.
Check Trans Indicator
The electronic control system of the
transmission is programmed to alert operator
of a problem with the transmission system, and
reacts automatically to protect the motorhome
and transmission from damage. Normally, the
Check Trans indicator on the speedometer LCD
will display when there is an error condition.
The indicator will go out after the engine
has started. The transmission system should
be checked immediately if the Check Trans
indicator displays. The Check Trans warning
indicates the ECU has detected a fault and
recorded a diagnostic code. The Check Trans
warning is accompanied by a
fl
ashing display
from the shift selector.
The shift selector display shows the actual
range attained and the transmission does not
respond to shift selector requests when the
ECU detects a Do Not Shift (DNS) condition.
Indications from the shift selector inform the
operator that the transmission is operating
at reduced capabilities. The transmission
generally will downshift to 4th gear. The torque
converter will not “lock-up” and engine speed
is automatically reduced. Direction changes (i.e.
forward to reverse) are not allowed. This allows
time to
fi
nd a safe place to park the motorhome
to prevent transmission damage. If the engine
is shut off, then started after a Check Trans
indication, the transmission remains in Neutral
until the fault has been corrected. Service should
be performed immediately in order to minimize
potential damage to the transmission.
NOTE:
Contact an authorized Allison
Transmission service center whenever
a transmission related concern arises.
For some problems, fault codes
may be registered without the ECU
activating the Check Trans indicator. An
authorized Allison Transmission Service
center will have the equipment to check
diagnostic codes and correct problems
that may arise.
Diagnostic Codes:
The shift selector can be used to display
transmission malfunctions as numerical codes.
Each code is a two-digit main code and a
two-digit sub code. These codes will fall in
two classes: active and inactive. Active codes
are codes currently affecting the ECU process
and transmission operation. Inactive codes
are retained in memory but may not affect
the ECU process or transmission operation.
A service technician will activate Diagnostic
mode or hook an electronic display (Pro-Link)
to the data plug to retrieve diagnostic codes.
A maximum of
fi
ve codes, D1 to D5, may be
listed at one time. The highest priority code
will be listed in D1. The Mode button will
enable selection of sequential codes. Allison 4th
Generation controls list each code consisting of
fi
ve characters. The
fi
rst being a letter followed
by a four digit number string. The most severe
or recent code is listed in the ECU memory
fi
rst with a maximum of
fi
ve codes being d1 to
d5 possibly listed at the same time. When new
codes are added, the oldest inactive codes will
be dropped.
To Display Diagnostic Codes:
Stop the motorhome at a safe location.
Apply the parking brake.
Simultaneously press the up and down
arrows once to enter oil level display
mode. Then press the up and down
arrows again to enter diagnostic mode.
The codes will display one digit at a
time or two characters at a time on 4th
Generation controls.
Press the mode button to scroll through
the codes.
Record all diagnostic codes that are
displayed. The codes then can be used by
an Allison Service Center for evaluation
and repair.
Inactive codes can be cleared by holding
the Mode button for approximately three
seconds. 4th Generation controls require
holding the Mode button for ten seconds
to clear both inactive and active codes.
Some codes are self-clearing while others will
require service or ignition on/off cycles to clear.
