2006 MAF low signal code no 12v pin 2 to pin 3

Prometheus

Well-known member
Joined
May 11, 2006
Location
Long Island, NY
TDI
2006 5spd Jetta
So I have been driving around with my check engine light on because I have been ignoring the scan results. When I scanned the car it said MAF low signal. I had tried cleaning the MAF sensor with MAF sensor cleaner. Cleared the CEL and 5 minutes later it returned. Installed a brand new MAF unit, cleared the CEL code and again it returned. Out of frustration and knowing the next steps would be tracing wires I left things as is for a while. After all I did not notice any loss of power while accelerating so I was not overly concerned with the CEL.

Today I decided to start looking into this further. I took the MAF sensor leads off and tested the pins. I do get 5v from pin 3 to pin 4 with the car running. I do not get 12v from pin 2 to pin 3. If I researched correctly pin 2 is the 12v supply input to the MAF sensor. So it would make perfect sense that it is throwing low signal codes if the MAF sensor has no supply voltage. I traced the supply input wire back to the fuse box and it seems to be visually intact. I changed the relay marked with 458 ("relay 109") which I believe is connected to the supply line with no luck of getting 12v on pin 2 to pin 3. I also tried stripping some insulation off 6 inches back of the plug on the supply line to make sure the plug connector terminals are not the issue. No luck getting any voltage reading that way.

Questions:

1) Am I correct in wanting to read 12v from pin 2 to pin 3 from the MAF sensor wires while the car is running?

2) Being a supply line I assumed I do not need to apply some acceleration for a reading. Is that a safe assumption?

3) Has anyone traced the lack of 12v back to a common problem area? Is there a bend or pinch area that is well known to cause a loss of voltage?

Thanks for any feedback.
 
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