Ok, the background of why I am asking this. I acquired a 1991 Grand Prix with the 3.1 and OD Tranny. The prior owner removed the stock airbox and shoved a cone filter into said hole. I fixed the filter up but I still have a sensor hanging there. My service manual says it is a MAT sensor. My question is what is that?

Welcome to AF.

MAT?? MAF maybe. Mass Airflow Sensor or Intake Air Temperature (IAT) sensor. MAF sends airflow data to the ECM module to help with the proper fuel injection system air/fuel mixture ratio. IAT is a sensor to let the ECM module know the temperature of air intake. On most GM engines the MAF can be disconnected and driveability could be normal except it may not switch into closed loop mode.

Thanks for the reply BNaylor, I have been just a bit confused with all these 3 letter sensors. I could see the IAT explanation because of where it looks like it is located on the filter box. The local branch of Autozone is telling me my car doesnt have a MAF, it has a MAP sensor. :banghead: All I know is that this car has 263k miles, it was free and I am having fun.

You're welcome.

Sounds about right to me. According to my documentation the Vin "T" 3.1 V6 doesn't have a MAF sensor listed. It didn't get one until the Vin "M" version of the 3.1L came out a few years later.