Diagnostic Aids

WARNING: This page is about a different car, the 2020 Cadillac CT6. However, it is still accessible from the selected car via links, so may be relevant.

It is critical to use the service replacement Communication Interface Module only in the vehicle for which it was ordered.
Failure to perform the following procedures will result in a red LED, DTC(s) being set, and limited or incomplete OnStar® services.
A test call is required to complete the procedure.
On vehicles up fitted with TTY capabilities, it is necessary to perform a power cycle of the OnStar® Interface Module (OTIM), and toggle the TTY mode after completing the Communication Interface Module installation and setup procedures.