Encoder Switch Monitor Check

While the transfer case is shifting, the position encoder switch within the electric-shift motor is monitored for the proper operating sequence. If at any time during a shift, the encoder changes to a condition other than the next possible position, an error counter in the TCCM is incremented by four. After the counter reaches 32, DTC 2 (Encoder Fault) is outputted and the TCCM reverts to a default rail-to-rail shift pattern in which only shifts into 2HI and 4LO are possible.

To protect against transient, random encoder faults caused by vibration, contamination, electrical noise, etc., the fault counter is reduced by one each time a good encoder value is detected. Thus, the encoder must fail 25 percent of the time to be considered permanently bad and store a DTC 2.