2000 Ford Windstar with codes PO171 and PO174

2000 Ford Windstar, 3.8L V6, 136,000 miles, Changed all four of the 02 sensors and IAC motor, MAFS, fuel filter and checked and replaced vaccum lines. Intake manifold was leaking just a little so I went ahead and replaced the gaskets and cleaned the injectors. When I have the computer on it reading live data the MAFS is reading 0.00(lbs/min) all the time, this is why I replaced it the first time thinking that was the problem... did I get a bad part or is this normal? I took it for a drive and this number never comes off of 0.00. I am going to get some fuel pressure readings and post back ASAP. Thanks for the help!


(This post was edited by Atbennett87 on Jan 19, 2010, 1:25 PM)
You will need a digital multimeter set to the 20 volt dc scale. Unplug the MAF sensor connector and put the red probe in terminal 2 (red wire) and black probe in terminal 3 (blk/wht wire). With key on engine off you should have battery voltage. If no voltage, leave red probe in term 2 and move black probe to any engine ground. If you now have battery voltage repair open blk/wht wire between MAF sensor and PCM. Please post back after these voltage tests so we can go further.

Steve
Tested with meter and got battery voltage using terminal 2+3, Thanks
                       MAF SENSOR: Terminal 1: GRY/RD - I.A.T. signal return, goes to ground splice
2: RD MAF Power
3: Blk/Wht MAF Power Ground
4: TN/LB MAF Signal Return, goes to term. 36 of PCM
5: LB/RD MAF Signal, goes to (looks like) term 38 of PCM
6: GY IAT Goes to term 39 of PCM
A good place to start here would be to do continuity tests of all the wires from the MAF connector to the PCM connector. If all wires ring out good then reconnect PCM connector. Turn the key on engine off and test the MAF sensor connector term 5 to ground, should be approx. 5v dc. If all tests good, you will need to re-connect MAF connector. Carefully backprobe MAF terminal 4 with the red lead, black connected to ground. Set meter to 20 volts AC scale. the reason for AC is because the MAF sensor outputs an analog signal rather than a digital signal to the PCM. If you have a hand held lab scope this would be perfect. Start engine. Observe voltage as you slowly but gradually increase engine speed. The voltage should rise smoothly with RPM increase. If OK, sensor working fine, possible PCM failure or calibration code update required. If voltage no good, replace MAF sensor.

Steve