Sorry to hear about the issue with the key FOB. The remote keyless system operates on a radio frequency between the FOB and vehicle. There is a re-learn process outlined in the Owner's Manual on page 197. If these steps don't work, please take it back to the dealer where the FOB was purchased and advise them of the situation. If the vehicle is returned to the dealer, the phone# for GM Customer Service is 800-222-1020 with hours of: Mon to Sat, 8am to 9pm ET. You can send an e-mail to firstname.lastname@example.org with the VIN#, customer name, contact information, situation, name of dealer, and current mileage. Please address it to me. Thank you and I hope this situation is resolved quickly.
Steps from Owner Manual on page 197, located under the DIC guide starting on page 193.
RELEARN REMOTE KEY
This display allows you to match the Remote
Keyless Entry (RKE) transmitter to your vehicle.
To match a RKE transmitter to your vehicle,
do the following:
1. Make sure the vehicle is in PARK (P).
2. Press the vehicle information button until
PRESS V TO RELEARN REMOTE KEY
3. Press the set/reset button.
The message REMOTE KEY LEARNING
ACTIVE will display.
4. Press and hold the lock and unlock buttons
on the first transmitter at the same time for
about 15 seconds.
A chime will sound indicating that the
transmitter is matched.
5. To match additional transmitters at this time,
repeat Step 3.
Each vehicle can have a maximum of
four transmitters matched to it.
6. To exit the programming mode, you must
cycle the key to LOCK.
GM Customer Assistance