Trying to identify the cause of a mass air flow sensor problem. Testing for power to the sensor with the ignition switch on and did not have 12 vdc on the power terminal when back probed. Where does the mass air flow sensor get it power from? Could not find a diagram on the internet.

 

Welcome to site..

What model?

 

2004 Ford Explorer, XLT, automatic.

 

Hot in Start/Run input comes from Battery Junction Box fuse F1.40~15 amp Fuse.
MAF connnectir Pin #6 ~ wire color Violet is battery voltage switched...

 

Thanks for the information. I was led to believe it was #5 wire. Good reason not to get 12v. I do have 12 volts on #6. What would the normal voltage range for the other pins when running?

 

4.0 or 4.6? just so we're on the same page.

Guessing 4.0

Pin 1 5v VREF (signal) from PCM to Air Charge Temp Sensor
Pin 2 Signal Return from ACT to PCM
Pin 3 MAF sensor output (hot idle .7-.9 DCV)
Pin 4 MAF signal return
Pin 5 Ground
Pin 6 12v in Run/Start

 

Your guess of 4.0 is correct. From what you gave as numbers and compared to what I recorded, I need a new MAF sensor.
Pin 1 1.75
Pin 2 .04 - .05
Pin 3 0.00
Pin 4 .01 - .02
Pin 5 Validated gnd.
Pin 6 13.8 v All readings were taken with the engine hot and running.

Thank you so very much for your help and putting up with me.

 

You never said why you suspected the MAF? Any DTCs to support the concern?
That VREF is low, tested back probing or piercing the wire insulator? MAF disconnected, is the VREF still that value? Cause for a low VREF can be many since its generally a shared PCM output voltage with other components..

 

First things first. I have tested with a back probe and wire piercing - still the same readings. With the MAF disconnected, pin 1 reads 4.85 volts. As for what made me think it was the MAF. A friend of mine told me that it was probably the MAF. This thing has been throwing codes and I have been replacing parts to no avail. These are some of the codes PO107 3 times, PO104 3times, PO201 2times, PO221 1time, PO102 1time, P2106 1time.
I have blown off and cleaned the MAF with a spray, Cleaned the TPS, Replaced the throttle body, Replaced the TPPS, Cleaned the fuel injector and finally replaced it.
Now I have replaced the MAF sensor, cleared the codes - After driving about 35 miles, I am coming up with a PO401 code - EGR flow insufficient