CHECK TRANS LIGHT
The electronic control system is programmed to inform the operator of a problem
with the transmission system and automatically take action to protect the operator,
vehicle, and transmission. When the Electronic Control Unit (ECU) or the
Transmission Control Module (TCM) detects a problem condition, the TCM/ECU:
• Restricts shifting.
• Illuminates the CHECK TRANS light on the instrument panel.
• Registers a diagnostic code.
NOTE: For some problems, diagnostic codes may be registered without
the TCM/ECU activating the CHECK TRANS light. Your Allison
Transmission authorized service outlet should be consulted whenever
there is a transmission-related concern. They have the equipment to
check for diagnostic codes and to correct problems which arise.
Each time the engine is started, the CHECK TRANS light will illuminate, then
turn off after a few seconds. This momentary lighting is to show that the status
light circuits are working properly. If the CHECK TRANS light does not
illuminate during ignition, or if the light remains on after ignition, the system
should be checked immediately.
Continued illumination of the CHECK TRANS light during vehicle operation
(other than start-up) indicates that the TCM/ECU has signaled a diagnostic code.
Illumination of the CHECK TRANS light is accompanied by a flashing display
from the shift selector. The shift selector display will show the actual range
attained and the transmission will not respond to shift selector requests.
Indications from the shift selector are provided to inform the operator the
transmission is not performing as designed and is operating in the “limp home”
mode with reduced capabilities. Before turning off the ignition, the transmission
may be operated for a short time in the selected range in order to “limp home” for
service assistance. Service should be performed immediately in order to minimize
the potential for damage to the transmission.
DRIVING TIPS
31
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