Circuit Description
The transfer case encoder motor is an assembly which houses 4 separate channels. These channels are used to indicate to the transfer case shift control module (TCCM) 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 3 legged wiper arm. Each leg's length is such that it makes contact with the conductive regions of the 4 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 TCCM 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 TCCM increments by 4. After the counter reaches 32, the TCCM sets a DTC 002, a permanent "encoder fault," and reverts to a 2HI to 4LO or a 4LO 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 TCCM detects a valid encoder value. The encoder must intermittently fail 25 percent of the time for the TCCM to consider it faulty and store DTC 002. It is imperative that the technician test-drive the vehicle and request several shifts in order for this code to properly be set.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC 002 Encoder Circuit Malfunction
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.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step measures the voltage between the transfer case encoder circuit channels P, A, B, and C to ground.
-
This step tests the suspect circuit for an open, short to power, or short to ground.
-
This step tests the encoder signal ground circuit for an open or high resistance.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Transfer Case Control Schematics | ||||
1 |
Important: Check the transfer case shift control module for DTCs. The transfer case shift control module is not a class 2 device. DTCs are displayed on the transfer case shift control switch. Use the following 4 steps to obtain
DTCs.
Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
Does the voltage measure near the specified value? | 4.8-5.1 V | Go to Step 4 | Go to Step 3 | |
Test the suspect circuit for an open, short to power, or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 7 | |
Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 5 | |
5 | With a DMM at the transfer case module connector probe the encoder sign ground pin and ensure a good ground path through the module. Did the DMM indicate a good ground path? | -- | Go to Step 6 | Go to Step 7 |
6 | Replace the transfer case encoder motor. Refer to Transfer Case Motor/Encoder Replacement . Did you complete the replacement? | -- | Go to Step 8 | -- |
7 | Replace the TCCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 8 | -- |
8 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
