SHIFT SEQUENCES
Once all the driver controllable conditions for the requested shift have been met, the TCCM begins a shift timer with
a maximum duration of 1 second per ’D’ channel transition. If the shift timer expires before the TCCM recognizes to
correct mode sensor code, the shift is considered to have been blocked. The blocked shift will increment the
blocked shift counter by one. The TCCM strategy for handling blocked shifts will be described later. The process the
TCCM performs for the various shifts will be described first.
RANGE AND MODE SHIFTS
The process for performing all the range and mode shifts are the same. The following steps describe the process.
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Allow time for Selector Switch debounce; 250 msec ±50 msec.
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Extinguish the source gear’s LED while flashing desired transfer case position’s LED.
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Engage the shift motor for a maximum of 1 second ±100 msec per ’D’ channel transition in the destination
gear’s direction while monitoring the mode sensor channel transitions.
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Disengage the shift motor when the correct mode sensor code is recognized.
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Solidly illuminate the selected gear’s LED.
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Transmit a bus message that the transfer case shift is complete.
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If the desired mode sensor code is not received after the shift timer expires (ie. a blocked or other condition
exists), stop driving the motor and wait for 200 msec ±50 msec. The shift motor is then reversed in the direc-
tion back toward the source gear for up to 1.0 seconds ±100 msec. per ’D’ channel. The TCCM waits for 2.0
seconds ±50 msec. and repeats the attempt to shift to the desired position.
The exception to the preceding sequence is when a shift from 4L to 2WD/AWD is requested. If 2WD/AWD is
requested from the 4L position, the transfer case is first driven to the 4H position. If the 4H position is reached, the
transfer case is then driven back to the 2WD/AWD position and the shift is considered complete. If the transfer case
does not reach any the 4H position, but is in the 2WD/AWD ’D’ channel, or the 2WD/AWD between gear position on
the 4H side of 2WD/AWD, the shift is also considered complete.
SHIFT OUT OF NEUTRAL
The following steps describe the process for a shift out of NEUTRAL.
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Extinguish the Neutral LED.
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Engage the shift motor for a maximum of 1 second ±100 msec toward the transfer case 4H mode position
while monitoring the mode sensor channel transitions.
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Disengage the shift motor when the correct mode sensor code is recognized.
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Extinguish the Neutral LED.
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Transmit a bus message that the transfer case shift is complete.
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If the desired mode sensor code is not received after the shift timer expires (ie. a blocked or other condition
exists), stop driving the motor and wait for 200 msec ±50 msec. The shift motor is then reversed in the direc-
tion back toward the source gear for up to 1.0 seconds 100 msec. The TCCM waits for 2.0 seconds ±50 msec.
and repeats the attempt to shift to the desired position.
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When the Neutral button is released, if the 4H position is the desired position, the shift is complete. Illuminate
the 4H LED.
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Otherwise when the Neutral button is released, if all of the shift requirements are being met then engage the
shift motor towards the desired position for 1 second ±100 msec per ’D’ channel. (if requirements for shifting
are not met, illuminate the 4H LED and flash the destination LED as an indication to the driver that all of the
driver controllable shift conditions are not being met). If this requires another range or mode shift, begin the
range/mode shift process.
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If the desired mode sensor code is not received after the shift timer expires (i.e. a blocked or other condition
exists), refer to the section on Blocked Shift Strategy.
BLOCKED SHIFT STRATEGY
When a shift is commanded, the shift motor will be driven towards its destination position, except in the case of
shifting out of Neutral if 4L was selected (the transfer case will shift to the 4H position first, before proceeding to 4L).
If the shift is blocked on the way to the destination, the TCCM may attempt to drive the motor back to the original
position. This process will be allowed to occur 5 times. If the transfer case has reached a non-NEUTRAL ’D’ chan-
nel during the shift re-attempts, the LED for the achieved gear position is illuminated and the shift attempts are
8E - 136
ELECTRONIC CONTROL MODULES - SERVICE INFORMATION
DR/DH