Interesting Maf sensor info

[Legacy777]

Well i found some interesting things today.

I bought vrg3's spare MAF sensor. After having a few discussions that oil based filters cause issues with the MAF by creating buildup on them I wanted to swap MAF's.

I cleaned vrg3's sensor with brake cleaner just so I had a "baseline" clean to work with. Well when I was switching sensors, I noticed something weird. The new sensor I had purchased back in 01 did not have a pin 5, which looks like 5v reference voltage from the ECU. The sensor vrg3 sent me had the 5th pin. Both MAF's have the same part #.

Not sure why this is like this. I'll be curious to see how the car runs. I'm in the process of resetting the ECU. We'll see how things are.

Anyone have any ideas why one sensor only has 4-pins and the other has 5-pins.

here's pics

FSM MAF Diagram:
http://www.main.experiencetherave.com:8 ... sting1.jpg


4-pin MAF sensor
http://www.main.experiencetherave.com:8 ... rpins3.jpg

5-pin MAF sensor
http://www.main.experiencetherave.com:8 ... rpins1.jpg
http://www.main.experiencetherave.com:8 ... rpins2.jpg

[vrg3]

The 5th pin isn't used on plastic-bodied MAF sensors.

At some point they started including that pin in the connector... I think it was around 1996. The sensor I sent you came off a 1997 Outback if I remember right. But you say you got yours new in 2001 -- do you know if it was new old stock?

It's unusual that they made a change to the part without incrementing the part's revision number, but they did. However, functionally there is no difference. If you took apart the sensor I sent you you'd find that pin 5 goes nowhere internally (don't do that, though, since you won't be able to reassemble it). It may just have been an assembly line optimization change.

That pin is used by the metal-bodied sensors. I agree with your guess that it's a 5-volt reference that would allow for more precise airflow readings.