Flash: Drivetrain Control Module (DTCM) Diagnostic and System Improvements This bulletin involves...

Bulletin number

08-067-21

Component

Exterior lighting

Summary

Flash: Drivetrain Control Module (DTCM) Diagnostic and System Improvements This bulletin involves reprogramming the DTCM with the latest available software. The technician may find one or more of the following DTCs:U1440 - Implausible Transfer Case Ratio High Received. U0403-00 - Implausible Data Received From T-case. C1403-92 - Transfer Case Range Position Sensor-Performance Or Incorrect Operation(2019-2020 Vehicles Only). If only DTC C1403 is present, follow normal diagnostic procedures before updatingthe DTCM.In addition the customer may describe one or more of the following:Traction Control System light is illuminated. A driveline bump can be heard/felt occasionally when the driver is steady on the throttle at about 20-30% on a flat road while in 4WDAUTO(2019-2020 Vehicles Only). An excessive electric motor clicking sound from the middle of the vehicle/transfer case area, when on and off the throttle(2019-2020 Vehicles Only). An excessive electric motor clicking sound with steering wheel movement, most notable in parking lot or low speed maneuvering(2019-2020 Vehicles Only). A ?Service 4WD? message/fault without commanding a transfer case shift(2019-2020 Vehicles Only).If only the ?Service 4WD? message/fault is displayed in the Instrument Panel Cluster (IPC) and no other symptom/conditionsare present, follow normal diagnostic procedures before updating the DTCM(2019-2020 Vehicles Only). The blinking of the ?4WD Low? and ?4WD High? indicator lights at the same time, on the transfer case selector switch.If both 4WD indicator lights on the transfer case selector switch are blinking and no other symptom/conditions are present,follow normal diagnostic procedures before updating the DTCM(2019-2020 Vehicles Only). During highway/freeway speeds, a bump in the driveline may be felt. This could also be described as a harsh transmission shift(2019-2020 Vehicles Only).

Owners of these vehicles have filed 57 complaints in the lights category.