To be certain, you should:
1. Consult a repair manual specific to your 1996 Pontiac Grand Am GT. This is the most reliable way to pinpoint the sensor's location. The manual will have diagrams and detailed descriptions.
2. Check online forums or resources specific to Pontiac Grand Ams. Someone may have posted a picture or description of the location.
Keep in mind that accessing this sensor will likely require some work underneath the vehicle. Be prepared to get dirty and have the necessary tools.