quote:

1. The diagnostic trouble codes are displayed on the three transfer case shift select buttons. The shift select buttons are located to the right of the instrument panel cluster. When pin 13 of the data link connector is grounded and the ignition switch has been in the OFF position for at least five seconds prior to positioning the ignition switch to the RUN position, the shift select buttons will blink a number of times in order to indicate a diagnostic trouble code from 1 to 4.
   1. Position the ignition switch to OFF.
      Ensure the ignition switch is positioned to OFF for at least 5 seconds.
      
   2. Connect pin 13 on the data link connector to a vehicle ground source.
      The data link connector is located in the cab under the instrument panel on the drivers side.
      
   3. Position the ignition switch to RUN.
      
   4. Note the shift select buttons for blinking codes. Refer to Perform a Diagnostic on the TCCM.
   
   
2. If the shift select buttons all blink one time and stop, and do not continue to blink, no fault codes are stored in the TCCM.
   
3. The transfer case shift select buttons will blink in order to identify any stored DTC. If only one code is stored in the TCCM memory, that code will blink repeatedly with a three second delay between blinking sequences. If more than one code is stored, the first code will blink once, then after a three seconds delay, the next code will blink. This sequence will continue until pin 13 is no longer grounded.
   
4. When reading the diagnostic trouble codes, the number of shift select buttons blinks will indicate the code number.

quote:

Important: The codes will not clear if the 15-amp 4WD fuse is not removed for at least 30 seconds.
The code 1 will continue to occur until the ignition switch is cycled from RUN to OFF five times.

1. Perform the following in order to clear the Diagnostic Trouble Codes (DTC) and in order to clear the stored memory from the Transfer Case Control Module (TCCM) .
   
2. Turn the ignition switch to the OFF position.
   
3. Remove the 15-amp 4WD fuse.
   
4. Wait at least 40 seconds then replace the fuse.
   
5. Cycle the ignition switch from RUN to OFF five times in order to clear the diagnostic trouble code 1 from the TCCM.

quote:

DIAGNOSTIC CHART

CIRCUIT DESCRIPTION
The transfer case shift control module normally has battery voltage supplied to it at all times through the battery positive voltage circuit (CKT 40). When the ignition is ON, the transfer case shift control module conducts a self-test to determine if it retains the same memory it had when the ignition was last turned OFF. This self-test indicates whether the RAM standby power supply to the transfer case shift control module pin C6 was interrupted, which would result in clearing DTC''''''''s from memory. If the self-test fails the transfer case shift control module sets DTC 1.

CONDITIONS FOR CLEARING THE DTC
This DTC will clear when the voltage supply failure has been corrected and the ignition switch has been cycled five times.

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
2. This step inspects the CTSY LP fuse for an open.
3. This step test the battery positive voltage circuit (CKT 40) for an open or high resistance.
4. This step rechecks the CTSY LP fuse for an open
5. This step tests the battery positive voltage circuit (CKT 40) for a short to ground.

quote:

DIAGNOSTIC CHART

CIRCUIT DESCRIPTION
The transfer case encoder motor is an assembly which houses four separate channels. These channels are used to indicate to the transfer case shift control module the present gear position of the transfer case or if the transfer case is in transition between gears. The encoder motor assembly consists of an electronically conductive inner ground ring in contact with a three legged wiper arm. Each leg''''''''s length is such that it makes contact with the conductive regions of the four channels. When any leg of the wiper arm is making contact with the conductive area of any channel, the encoder provides a path to ground to the inner ground ring.
During electronic shifting, the transfer case shift control module monitors the transfer case encoder circuit for the proper operating sequence. If at any time during a shift, the encoder changes from one position to any position other than the next possible position, an error counter in the transfer case shift control module increments by four. After the counter reaches 32, the transfer case shift control module set a DTC 2, a permanent "encoder fault," and reverts to a 2HI to 4L0 or a 4L0 to 2HI shift pattern only. To guard against a transient, random encoder fault due to vibration, dirt, electrical noise, etc., the fault counter reduces by one each time the transfer case shift control module detects a valid encoder value. The encoder must intermittently fail 25 percent of the time for the transfer case shift control module to consider it faulty and store DTC 2.

CONDITIONS FOR CLEARING THE DTC
The condition for setting the DTC is no longer present and a momentary loss of battery power at the battery positive voltage circuit (CKT 40).

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
2. This step measures the voltage between the transfer case encoder circuit channels P, A, B, and C to ground.
3. This step tests the suspect circuit(s) for an open, short to power, or short to ground.
4. This step tests the encoder signal ground circuit for an open or high resistance.

quote:

DIAGNOSTIC CHART

CIRCUIT DESCRIPTION
The transfer case encoder motor has a bi-directional, permanent magnet, D.C. motor. When energized, (through Motor Control A or Motor Control B, the ground is provided by the opposing motor control circuit and then grounded through the transfer case shift control module ground circuit), the motor, through a series of gears, rotates a shaft which moves the mode and range forks to shift the transfer case between 4H, 2HI, and 4L ranges.
This DTC detects a short or open in the battery positive voltage circuit (CKT 1640), ground circuit, an internal short in the motor windings and related circuitry, or an internal transfer case shift control module failure.

ACTION TAKEN WHEN THE DTC SETS
In the event that one of the motor control circuits is energized (battery voltage is applied) the transfer case shift control module will energize the other motor control circuit to keep the motor from running. All switch indicator lamps will flash continuously to prompt the driver that service is required. The transfer case system will be disabled and the transfer case shift control module will remain energized even with the ignition in the OFF position.

CONDITIONS FOR CLEARING THE DTC
The condition for setting the DTC is no longer present and a momentary loss of battery power at the battery positive voltage circuit (CKT 40).

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
2. This step tests the battery positive voltage circuit (CKT 1640) for an open or high resistance.
3. This step inspects the ATC fuse for an open.
6. This step tests the ground circuit.
8. This step tests the Motor Control A and B circuits.

quote:

DIAGNOSTIC CHART

CIRCUIT DESCRIPTION
At each power up the transfer case shift control module runs a self test on the following:
* EEPROM Checksum
* ROM Checksum
* RAM Checksum
* RAM Malfunction

CONDITIONS FOR RUNNING THE DTC
* Critical operational parameters stored in EEPROM have failed Checksum test indicating invalid data.
* Masked ROM code has failed Checksum test indicating that masked ROM data is no longer valid.
* ROM code has failed Checksum test indicating that ROM data is no longer valid.
* One or more ROM locations have failed operational test indicating that some portions of RAM are not functional.

CONDITIONS FOR CLEARING THE DTC
The condition for setting the DTC is no longer present and a momentary loss of battery power at the battery positive voltage circuit (CKT 40).

DIAGNOSTIC AIDS

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
2. This step replaces the transfer case shift control module.