MAF pinout GA16DE

Hello.

Anyone know the MAF sensor pinouts on the 1.6 liter sentra (GA16DE) engine. the only ones i found are for the 2.0 liter and it has 3 wires for the MAF, but mine has 4. i know one is for 12V reference, one ground, and one signal, don't know what the 4th one is for.
i apreciate any replies.

sensor side pins are arranged like this:


|1|2|3|4|

thanks