Diagnostic Aids

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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.