Hombre S Regular Cab 4WD V6-4.3L (1999)
Control Module: Description and Operation
Transfer Case Control Module Description
1. The TCCM performs the following functions:
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Receives input signals
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Processes the signal information
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Develops output signals
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Sends the output signal in order to control the shifting of the transfer case
2. The TCCM receives input signals from the following sources:
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The transfer case shift select buttons
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The NSBU switch on the vehicles with automatic transmissions
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The clutch position switch on the vehicles with manual transmissions
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The vehicle sped sensor calibrator module
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The encoder/motor range and the mode feedback signals
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The diagnostic enable
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The front axle mechanical status signal
3. In order to ensure the electronic shift system is operating properly,the transfer case control module (TCCM) continually performs diagnostics
checks on itself and other parts of the electronic shift system when the ignition switch is in the run position. The following are different types of
system checks that the TCCM continually performs.
RAM/ROM Check
The TCCM compares the current internal operating program with a stored operating program. This comparison allows the TCCM in order to evaluate
if the TCCM's RAM and ROM are operating properly. Should the TCCM detect a problem with the internal operating program, a diagnostic trouble
code (DTC) of 4 is stored indicating the TCCM memory is damaged. Replace the TCCM.
Data Memory Retention Check
The TCCM checks the stored diagnostic trouble code memory to see if the memory has changed since the ignition switch was last positioned to OFF.
This self test checks in order to see if the RAM standby power supply has been interrupted. If the TCCM detects a RAM standby power supply
interruption, (the loss of stored diagnostic trouble code) the TCCM stores a DTC of 1 indicating RAM standby power failure.
This condition occurs when the TCCM is disconnected from the wiring harness or battery power is removed. The DTC of 1 automatically clears from
the TCCM after cycling the ignition switch ON and OFF five times.
Encoder Signal Check
The TCCM checks the encoder signal in order to verify that the transfer case is in either 2H1, 4H1, or 4L0.
Encoder Switch Monitor Check
While the transfer case shifts, the encoder within the electric-shift motor is monitored for the proper operating sequence. If during a shift, the encoder
changes to an incorrect position, an error counter in the TCCM starts to count the number of times the encoder fails. If the encoder fails eight times,
the TCCM produces a DTC of 2 indicating an Encoder Fault. When this happens, the TCCM outputs a signal in order to default the rail shift pattern in
the encoder in order to allow for only shifts into 2HI and 4LO.
In order to protect against transient, random encoder faults caused by vibration, contamination, electrical noise, etc., the error counter reduces the
count by one each time a good encoder value is detected. The encoder must fail 25 percent of the time for the TCCM to store a DTC of 2 and indicate
a damaged encoder.
Encoder Switch Monitor Check
While the transfer case shifts, the encoder within the electric-shift motor is monitored for the proper operating sequence. If during a shift, the encoder
changes to an incorrect position, an error counter in the TCCM starts to count the number of times the encoder fails. If the encoder fails eight times,
the TCCM produces a DTC of 2 indicating an Encoder Fault. When this happens, the TCCM outputs a signal in order to default the rail shift pattern in
the encoder in order to allow for only shifts into 2HI and 4LO.
In order to protect against transient, random encoder faults caused by vibration, contamination, electrical noise, etc., the error counter reduces the
count by one each time a good encoder value is detected. The encoder must fail 25 percent of the time for the TCCM to store a DTC of 2 and indicate
a damaged encoder.
