nevernamed

Hey everyone,

Is the raw MAF voltage available in the 32B program? I'm trying to get it mapped into the ALDL stream but I can't figure out the address. Looking at the hac file it seemed like 00 ED, 00 EF, and 00 EC would be possibilities but none of them seemed to work. I tried replacing the startup coolant temp at 07 71 with those addresses.

RBob

iTrader: (1)

Should be in location $ED. Note that this will only work if using an analog MAF.

Change location $76C from $5F to $ED. That should do it. Although I'm not positive if I checked a $32 or $32B BIN.

RBob.

tequilaboy

Here's what I've done to read the MAF voltage.

I used the existing fuel pressure voltage signal (rescaled for 5.1 volts for display purposes) and changed the A/D channel read for this signal from channel 6 to the MAF input pin instead on channel A. (Changed $60 to $A0 at address 286C/LE86C)

As RBob mentioned it is also stored in $ED after the normal A/D channel read.

Either method will work.

nevernamed

Thanks for the replies. I'm pretty sure that for 32B the location for startup coolant temp is $771. I was able to remap something into that location when I tried replacing $5F with $ED but it didn't look like a MAF voltage, it went down when the displayed MAF value went up. I'll try it again.

The other method is interesting, replacing the fuel pressure voltage with the MAF voltage, but doesn't the computer use the fuel pressure voltage for anything, or is it only reading it to display it on the ALDL line? Also, I'm confused about the way you listed the address 286C/LE86C. I found the 268C location with $60 but I don't know what you mean by LE86C.

Thanks again.

nevernamed

Ok, so I get the same thing with both methods, but something is wrong or am I missing something really stupid here?

Here is some data at idle at initial startup, what I have tried to map as MAF voltage does show a relationship to the MAF, but not in the way I would have expected:

Here is the raw data:

http://nevernamed.home.mchsi.com/MAFvsV.txt

RBob

iTrader: (1)

What equation are you using to change the ALDL data to a voltage reading?

Should be V = N * 0.0196

RBob.

nevernamed

Yes, that is that way I applied the equation. I'm not sure what else to try here.

RBob

iTrader: (1)

I downloaded some '87 Bins and $771 & $772 is correct for the startup temperature ALDL address.

I also disassembled an '87 BIN (ABUT) and checked the usage of $ED. It is a store of the analog MAF value. However, this is only true when the option bit for analog/digital MAF is set.

If this bit is cleared then what is stored at $ED and $EE is the inverse of the frequency of the MAF. Which would show what you are seeing.

Double check your calibration at address $14, b2 should be set at that location. ABUT has the value of $84 in address $14. The $04 part of $84 being b2.

Other then that I don't know what could be causing the issue.

RBob.

tequilaboy

I'm trying to understand what could be wrong with your set-up.

Are you seeing 5 volts with the MAF sensor connector open and ign on, before the MAF high fault is set? There is a 5 volt pull-up on the VMaf input circuit that you should be able to monitor. With the MAF connector open, the raw input should read 254 and you should see also see 5 volts to validate your measurement set-up. Shorting the signal wire to ground should result in 0 volts and 0 gm/sec for the raw input.

Could you have a MAF fault already set and are seeing the result of the defaut airflow signal in your data display instead of the real MAF voltage based signal? How does the unlimited raw MAF signal look? Does it follow either the MAF signal, the voltage or do something else like stay at 254 or 0?

I also wondered about the analog/digital maf switch setting. Which ecm pin are you using to input the MAF signal? And are you using an analog or digital MAF?

I took a look at the raw data again. I think your seeing the default airflow. The idle values appear to be too stable to be the real airflow. I would expect more random noise and not the same values for 10 consecutive samples or so.

nevernamed

Here's some more information on this. First the analog MAF bit. I checked address $14, it has the value $C4, so the analog MAF bit is set. This probably sounds dumb, but I think I have an analog MAF, that would be the kind with the hot wire anemometer right? I actually didn't know you could have a digital MAF in these.

As to the other questions about the unlimited flow and voltage level with the MAF unplugged (thanks for suggesting that). When the engine is running the unlimited flow follows the displayed MAF. With the key on and the MAF disconnected, the unlimted shows 254 and the raw voltage shows 0.2 V.

There were also two error flags before I disconnected the MAF, 42 and 51. The SES light doesn't come on when the engine is running though. So does that mean that I don't have a MAF fault, or can I have a MAF fault without the light being on?

Thanks for taking the time to help me with this

tequilaboy

Assuming that you're using TunerPro or TunerProRT, in the Definition Editor for your voltage display:

Do you have

Operation: Multiply([X*Factor]+Offset)
Factor: 0.02 (or 0.0196) Offset 0.00

Range High 255
Range Low 0

nevernamed

I dont know when that 51 error got set, but I cleared it and it doesn't come back. I don't know many details about that code, but the engine ran fine with no SES and I could communicate with the PROM.
----------
yep, I'm using tunerpro and that is the equation I have applied.

tequilaboy

Also is
Item: 8 Bit (1 Byte)

nevernamed

yep

tequilaboy

Sorry man, I don't know what else to suggest.

It does work as described in my case, but I'm using a different sensor (Ford 05+ slot style MAF) on a different A/D input circuit (MAP2 on Pin D8 which is not pulled up to 5 volts).

I've never actually tried it with the stock sensor, but I think it should work in the same manner.

nevernamed

I tried something different that seems to work. I jumpered off the MAF sensor at the input to the ECM and input that to the autoprom A/D. I was somewhat concerned that tapping into that line would upset the ECM measurement but it seems to be ok, the autoprom must have a high impedance input. Here is the result:



I don't know what's going on with mapping the MAF voltage in the program, it's very strange that both methods gave the same incorrect result. Anyways this seems to be a workaround.

tequilaboy

Sorry this isn't very legible, but if you can read it you can see the vmaf input circuit roughly in the center of the page. There is a pull up resistor and another 10k resistor. You are measuring the voltage before the 10 k resistor, the ecm sees the voltage after the 10 k resistor. This is a bit different than the circuit I'm using which includes a voltage divider and low-pass filter (map2). http://www.cruzers.com/~ludis/1227165schematic.html

nevernamed

So the fact that the measured V into the autoprom vs MAF agrees with the tables means that the current flowing in the circuit is really small? Otherwise they should have been offset by some amount, unless I have a scaling error in the autoprom that happened to be the same amount? Even if there is an offset, if I can quantify it this should be ok right? Or is tapping into that line a bad idea?

Thanks.