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Discussion Starter · #1 ·
I just pulled the codes on my car and this is a new one to me. What would cause my MAF to read below the minimum voltage?

I don't even know where to begin with this one. Please help.

I have a Pro-M 75mm mass air. I am going to try putting my stock one back on and see what happens but in the mean time I need some help.
 

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It could be a dirty element, it could be a bad connection, it could be you're a victim of the imprecise transfer function of the aftermarket meter.
 

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I just got this code along with a bad ECM code and it turned out to be a bad ground between my block and frame. My ground was completely melted!!
Also you can change the MAF voltage by "clocking" the meter. Backprobe wires C&D on the meter and check the voltage, it should be between .4-.6 you can twist the meter and change the voltage! I didn't believe it until I tried it.
It could also be a bad MAF

Trent
 

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Did you get the Remote Optimizer, too, or just the MAF? I got a bad Remote Optimizer on the first try and they replaced it for free.

If you have a digital voltmeter, you should be able to backprobe the connectors on the MAF to see what it's reading. This will tell you if it's the MAF or if it's the wiring. Of the four wires, one is BATTERY VOLTAGE (12-14), one is ground, one is VREF (about 5V), and one is signal return. Signal return voltage is what the code refers to and it should be around .7-.9V at idle and 3.4-4.5 at WOT.

Not sure what year your car is, but you can backprobe the newer ones with the connector plugged in by putting the (red) probe into the back of the connector where the harness wires go into it.
 

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Having read Trentk's post, I pulled out my book "How to Tune & Modify Ford Fuel Injection" by Ben Watson. It says to check the voltage at idle on ECA pin 50 (which should be the same as the MAF return, terminal D), which should be between .2V and 1.5V (wider range than I expected)

It also says to check for Battery Voltage between terminals A and B. This will catch either a bad ground or bad Battery Voltage connection.

To check the wires between the MAF and the computer, Terminal D maps to pin 50 of the computer and Terminal C connects to pin 9. These are direct connections, so the resistance in the wire between the terminal and the computer should be less than 5 ohms.

Hope this helps.
 

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Discussion Starter · #7 ·
Thanks, I will check the voltage tomorrow, unfortunately my meter is at my brother's house.

I bought the meter with the electronics. It is supposed to be calibrated for 19 lbs. injectors. Can I use the electronics off my stock MAF on the Pro-M? Will it work since I still have the 19 lbs. injectors?

What do I clean the elements with? Brake cleaner?

Thank you for all you quick replies. I really appreciate it.
 

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cleaning MAF

I don't know about brake cleaner, but I'd worry about the chemicals hurting the element. (It is a very useful thing, though.)

Radio shack sells a can of electronic parts cleaner that works.

I used caburetor cleaner once then blew it dry with a light (LIGHT) shot of compressed air. I have since come to the conclusion that it wasn't the best idea since it will probably leave a residue. I don't think it hurt anything when I did it though, and it was better than not cleaning it, IMO.

When you say "with the electronics", do you mean that you got the sensor (the electronic one) and the tube, or that you also got the "Remote Optimizer"? As I mentioned, my first Remote Optimizer was bad and I had to run without it for a couple weeks until they replaced it. I knew it was bad because it was not putting out any signal at all on D terminal. It also barely ran.
 

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I use carb cleaner to remove the deposits and brake cleaner to remove the carb cleaner residue. You won't believe what this does for some cars.
 

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Discussion Starter · #11 ·
Still get the code

Okay, I checked the voltage between A & B, it was about 13.5 volts. Checked voltage at idle on D, it was about .8. I did this with the car idling and the MAF plugged in. I got no reading from C. What is C supposed to read?

I then replaced the MAF with the stock one and reset the computer. The code still appeared.

Also, since I have been getting this code my exhaust fumes are terrible. And since this is a convertable, I have to do something about it.

INTP - that sounds like a good book to have, where can I pick one up? Barnes and Nobles?

Thanks again for any help.
 

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RE: book. I got mine at Border's. My local B&N has limited selection. You might try bn.com or amazon.com.

I had trouble finding what C should read. I thought it was VREF (~5V) but I could be wrong.

My hunch is that you have a problem with the wire for C between the MAF and the ECU (pin 9). You can test this by checking the resistance (key off) between the ECU and the MAF plug. It's a bit of an effort to find the wire at the ECU, but you need to do this test. While you're there, check the resistance between D and pin 50.

You could also test C and D to ground (key off) to make sure resistance is infinite (making sure the wire is not shorted to ground).
 

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Discussion Starter · #13 ·
INTP - Thanks, I went to the Barnes & Nobles site this morning and ordered the book. I will try to check the wire for C tonight.

Thanks again.
 

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Discussion Starter · #14 ·
:confused: Okay, I am officially confused now. (which is nothing particularly new by the way).

I checked my "C" and "D" wires from the computer to the sensor. Both were okay.

Well, let me back up a minute and tell you what I found and you guys just tell me if this is normal.

With the MAF plugged in:

Metering Red(A) to Black(B) - 13.5 volts
Metering Red/Blue(D) to Black(B) - 7.8 volts
Metering Yellow/Blue(C) to Black(B) - NOTHING

With the MAF UNplugged:

Metering Red(A) to Black(B) - 13.5 volts
Metering Red/Blue(D) to Black(B) - NOTHING
Metering Yellow/Blue(C) to Black(B) - 5.3 volts

The thing that is confusing me is the C & D reading differences when plugged and unplugged.

Can someone try to explain this to me. Is it because one is sending the reading and the other is receiving it or what?

I also reset my idle according to the instructions on the Pro-M site because it said that if the idle screw on the throttle body was set too high it could cause the code.

Anyway, again I would appreciate any input.
 

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The UNplugged readings are right.

No matter how you test (with key ON) A,B, and C should be the same. D is different because it's the return signal from the MAF.

UNplugged readings should be the same as KOEO.

D should be closer to .78 volts than 7.8 volts at idle.

Can you run a wire from D to the inside of the car? (you'll have to find a ground somewhere, like the outside of the lighter) See what your MAF is doing as you drive. Cruise at 60 should be around 2.5V and WOT at high RPM may go as high as 4.5V. These numbers aren't exact, I'm just curious what it does at 60 and how high it goes at WOT. Get someone to ride with you to read the meter and write things down.

This is strange...
 

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Does your car want to Die on you occasionally when you are coming to a stop if you dont keep your foot on the throttle? My GT also will throw on the CEL for like 3-5 seconds, say when Im shifting from 2nd to 3rd gear and let the motor descelerate..When I do push down on the throttle, it seems like theres absolutely NO spark whatsoever and it will Buck and carry of for about 3 seconds and the CEL will go Off and the car will run Fine...Never did figure that out with my old Combo...
 

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Bump for any new info, im getting this code at idle but the CEL goes off when go above 1000rpm(driving basically). It'll just pop back on when you come to a redlight/stop sign and when you get back in the gas it wants to stumble until you get back up to RPM. Going to check voltage and stuff on the wires tomorrow and hopefully clock the meter and get the right voltage at idle.
 

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i had the same problem.,..

it was fan wash...




try throwing some duct tape over the 50% of the filter that faces the fan..my code went away when i did that...


JC
 
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