See also:

OnStar Personal Identification Number (PIN)
A PIN is needed to access some of the OnStar services, like Remote Door Unlock and Stolen Vehicle Assistance. You will be prompted to change the PIN the first time when speaking with an Advisor. T ...

Ignition Transmission Lock Check
While parked, and with the parking brake set, try to turn the ignition to LOCK/OFF in each shift lever position. • The ignition should turn to LOCK/OFF only when the shift lever is in P (Park). †...

Transmission Messages
SERVICE TRANSMISSION This message displays if there is a problem with the transmission. See your dealer. SHIFT TO PARK This message displays when the transmission needs to be shifted to P (Park). ...