MAF Voltage 2.77 VDC at Idle...WTF???

[AeroCoupe]

I have a 2000GT MAF on my 93 Coupe with other mods. The SCT chip is programmed for the MAF. I just got the motor back in the car and started it only to get the engine light flashing with it running at idle. I pulled the codes and got a 66 on the second round of codes with the KOEO. I could not run a KOER as I did not want to run a fresh motor with this problem. I measured the voltage return back to the EEC with the engine running and it is 2.77 at idle at the wiring on the MAF. From the tables I have looked at this is not what I would expect at idle.

Here are the readings I am getting with a DVM:

Key On Engine Off
MAF Disconnected:
Lt Bl/Red - 5.76 V+
Red - 11.95 V+

MAF Connected:
Lt Bl/Red - 2.80 V+
Red - 11.95 V+

I have been told that a Code 66 (MAF signal below minimum test voltage of .4vdc [O,M,R]). Can anyone verify the voltage range at idle? It was also suggested that I check the wires at the ECM to see what the the MAFSIG wire has at the ECM as it appears that the circuit is open otherwise a code 56 should be the one showing with the voltage reading I currently have. From the wiring diagrams I have it appears that the Lt. Blue/Red wire is the MAFSIG wire as this is the one I am measuring the 5.76 and 2.8 V+ on. My wiring diagram shows the following:

Red - 12V+
Black - Ground
Light Blue/Red - MAF Sensor
Tan/Light Blue - MAF Sensor Return

I also have a wiring digram on converting the Fox MAF style connector to the newer on on the 2000GT MAF that I am currently running and have attached that.

I just went back out into the garage and measured the voltage at the EEC. I measured across PIN 9 and PIN 50 and came up with 2.743 V+. This is with the Key On Engine OFF and the MAF connected. I have the pin out of the 93 EEC connnector (from the dealership) that I used to locate the correct pins and the colors on these pins matched the ones in the wiring diagram.

PIN 9 - Tan/Lt. Blue
PIN 50 - Lt. Blue/Red

So are the MAF electronics FUBAR?

Darren

 

[AeroCoupe]

Just to clarify I cannot run the car without the SCT chip as it corrects for the 2000 GT MAF, the 24 lb/hr injectors, the cam, etc.

Darren

 

[Mike86Stang]

Sounds like your MAF is screwed... i ran into a similar problem with an old fox meter...bottom line after much cursing & confusion the MAF was bad.

 

[AeroCoupe]

That is what I am thinking. I am going to get a couple more from the salvage yard tomorrow and see what happens when I just plug another unit in. Frustrating as I have a lot of information between the EEC and the MAF but they are both black boxes to me as I have no idea what goes on with these signals between the two.

Darren

 

[AeroCoupe]

Well I finally got back in town and decided to look things over one more time and actually unwrap the wiring harness. Everything was just as it was supposed to be according to all of my notes. I went inside and began the wonderful task of getting caught up on paying bills when I found my answer. when I orginally wired the 2000 GT MAF into the car I wrote down how I wired it on a small piece of paper that came with the MAF wiring diagram. I was very glad that PMAS sent this piece of paper with the pigtail. I uncovered this piece of paper on my desk when I was paying bills and there it was staring at me...I had the MAF SIG and MAF RTN wires backwards. I went out into the garage and reversed these two wires on the MAF and after timing the car it runs very well. So the lesson here is always look for the simple stuff.

Darren