The P0633 code in your 2023 Chevrolet Traverse indicates that the immobilizer system has detected a key that isn't programmed to the vehicle. Modern vehicles require keys to be registered in the anti-theft system before they'll start the engine. If your key isn't recognized, P0633 is stored and starting is prevented.
How the Immobilizer System Works
Your Traverse uses a passive keyless entry and push-button start system. The key fob contains a transponder that communicates with the vehicle's immobilizer module. When you enter the vehicle with the fob and press start, the system verifies the fob's unique code against its stored list of authorized keys. Unrecognized fobs trigger P0633.
Why Key Programming Issues Occur
New or replacement key fobs require programming before use. Dealers and locksmiths must register the fob's code in the vehicle's system. If this step is incomplete, the fob won't be recognized. Battery replacement in the fob doesn't typically cause this issue, but complete fob failure might. ECM replacement can reset the authorized key list, requiring all fobs to be reprogrammed.
Symptoms You'll Experience
The engine won't start even though the fob unlocks the doors and appears to function. The security indicator may flash or remain illuminated. Push-button start doesn't respond or shows a key-not-detected message. If you have multiple fobs, testing each one determines if the issue is fob-specific or system-wide.
Resolution Process
Using GM GDS2, technicians program the key fob to the vehicle's immobilizer system. Each fob has a unique code that gets registered in the body control module. All working fobs must be present during programming. For new fobs, this is part of the normal setup process. After ECM replacement, all existing fobs may need re-registration.