Conditions for Setting the DTC
WARNING: This page is about a different car, the 2022 Cadillac CT4. However, it is still accessible from the selected car via links, so may be relevant.
C1135 13 or C1135 92
The differential control module detects a fault on the rear differential lock actuator motor circuit.
C1135 67, C1135 71, C1135 77, or C1135 98
The differential control module detects motor position incorrect.