What engine code reader will work with 1995 Pontiac Trans Am LT1?

Hello, the OBDII plug is likely something that body control components would utilize for testing, and maybe chassis. But for powertrain, you need to test the vehicle using OBDI procedures. I'm not sure there's a code reader that you can use, but if you do some searching online or with a workshop manual, you can find a way to make it work probably without a diagnostic tool. That said - OBDI is very primitive and you should be following symptoms to test for the source of concerns, unless a check engine light is on and you want to know what code is setting it off for troubleshooting. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops