K 1500 Suburban 4WD V8-5.7L VIN R (1997)
Transfer Case Actuator: Testing and Inspection
Encoder Switch Monitor Check
While the transfer case is shifting, the encoder within the electric-shift motor is monitored for the proper operating sequence. If during a shift, the
encoder changes to a 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 Transfer Case Control Module (TCCM) produces a DTC of 2 indicating a (Encoder Fault). When this happens, the TCCM outputs a signal to
default the rail shift pattern in the encoder to allow for only shifts into 2Hl and 4LO.
To protect against transient, random encoder faults caused by vibration, contamination, electrical noise, etc., the error counter reduces its count by one
each time a good encoder value is detected. The encoder must fail 25 percent of the time for TCCM to store a DTC of 2 and indicate a damaged encoder.
