Dodge RAM 1500 1998 Owner's Manual page 424

DR
TRANSFER CASE CONTROL MODULE (Continued)
• Proper transmit/receive messages are occurring
on the PCI bus.
• Ignition key switch is in the RUN position.
Range shifts will be allowed only if all of the fol-
lowing conditions are met:
• Front and rear wheel speed are within 21 km/hr
(13 mph).
• A change in the Selector Switch state indicating
a range shift has been requested.
• Transmission in NEUTRAL signal must be rec-
ognized for at least 1.5 seconds ±100 msec. (Auto-
matic transmissions only)
• Proper transmit/receive messages are occurring
on the PCI bus.
• Clutch signal is recognized for 500 msec ± 50
msec (Manual transmissions only).
• Vehicle speed is less than or equal to 4.8 km/hr
(3 miles per hour).
• Ignition key switch is in the RUN position.
• A valid mode sensor signal is being sensed by
the TCCM.
A shift into transfer case Neutral will be
allowed only if all of the following conditions are met:
• Front and rear wheel speed are within 21 km/hr
(13 mph).
• The recessed Neutral Selection switch has been
depressed continuously for 4.0 seconds ±100 msec
while all shift conditions have been continuously met.
• Transmission in NEUTRAL signal recognized
from the bus. (Automatic transmissions only)
• Clutch signal is recognized from the bus (Man-
ual transmissions only).
• Proper message transmissions/receptions are
occurring on the PCI bus.
• Vehicle speed is less than or equal to 4.8 km/hr
(3 miles per hour).
• Ignition key switch is in the RUN position,
engine off.
• Foot Brake is applied.
• A valid mode sensor signal is being sensed by
the TCCM.
A shift out of transfer case Neutral will be
allowed only if all of the following conditions are met:
• Front and rear wheel speed are within 21 km/hr
(13 mph).
• The recessed Neutral Selection switch has been
depressed continuously for 1.0 seconds ±100 msec
while all shift conditions have been continuously met.
• Transmission in NEUTRAL signal recognized
from the bus.(Automatic transmissions only)
• Clutch signal is recognized from the bus (Man-
ual transmissions only).
• Proper message transmissions/receptions are
occurring on the PCI bus.
• Vehicle speed is less than or equal to 4.8 km/hr
(3 miles per hour).
ELECTRONIC CONTROL MODULES
• Ignition key switch is in the RUN position.
• Foot Brake is applied.
• A valid mode sensor signal is being sensed by
the TCCM.
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.
• Allow time for Selector Switch debounce; 250
msec ±50 msec.
• Extinguish the source gear's LED while flashing
desired transfer case position's LED.
• Engage the shift motor for a maximum of 1 sec-
ond ±100 msec per 'D' channel transition in the des-
tination gear's direction while monitoring the mode
sensor channel transitions.
• Disengage the shift motor when the correct
mode sensor code is recognized.
• Solidly illuminate the selected gear's LED.
• Transmit a bus message that the transfer case
shift is complete.
• 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 direction 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 posi-
tion 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.
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