zero2005

Just wondering if anyone would happen to know or have the resistance/temp values for the intake air temp sensor located in the MAF?

i'm running a PMAS pro-tube, but the print-out i have doesnt state anything about the temp other than the temp it was calibrated at. i'm assuming that for the temp sensor they just used a stock ford type sensor.

also wondering about the wiring on the MAF for the 2 pins used for the temp, i know that A-D are for the MAF, and that E/F are for the temp sensor. but which one is ground?

edit: megasquirt also mentions a bias resistor, i'm assuming that 2490.0 will work.

I did find a table for a '00 taurus MAF. not sure if its correct or not? were all ford air temp sensors the same?

cliffyk

Here are the numbers you are looking for, per the '03 shop manual. All temperature sensors (IAT, ECT, and EOT) have this same curve (the chart presented for the CHT is so similar as to be statistically the same):



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The Voltage value qualifiers, "w/o resistor" and "w/ resistor" refer to measurement of the voltage with the sensor's output disconnected from the PCM, or measurement via "back-probing" which would be connected to the PCM.
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The manual also states that the voltage values shown may vary by as much as 15% dependent upon actual Vref and sensor variations.

This is not as scary as it sounds, because of the adaptive learning algorithms within the PCM it is repeatability of the reading that is more important than the absolute accuracy--and the Vref and sensor characteristics of any single vehicle are stable.

cliffyk

Whoops,

Here's the pinout for the stock MAF:



As you can see pins 2 through 5 are for the MAF, with only pin 3 being a true chassis ground.

The IAT sensor is wired in series between the non-Vref end of an internal (to the PCM) bias resistor and connection N, which is the signal "return" to the PCM--an internal to the PCM ground reference, NOT a chassis ground.



I should have looked at the diagrams rather than relying on memory above--the w/o resistor and w/ resistor description I provided above obviously has nothing to do with "connected" or "disconnected"--perhaps on some configurations there is an external bias or other resistor, IDK.

FWIW, based on a bit of reverse engineering I would guesstimate the internal bias resistor to be in the vicinity of 22kΩ...

zero2005

interessting. thanks.
i'll be sure to do a combined write up for anyone interested in doing a megasquirt. there's very little info out there on some of the things i'm doing. i'll be using a GM Coolant sensor, probably using the ford IAT sensor in the MAF, as well as future plans to use the MAF at the very least for data logging or low RPM control. just managed to get my LS1 coils temporarily installed (future plans for LS2 coils) for a "first start" hopefully by the end of this week.

if i had known that most ford temp sensors use the same ohms/degree value, i would have kept the ford coolant sensor, would have saved me $40. i grabbed both GM sensors, IAT and CLT, just in case. GM CLT threads directly into the ford port on PI intakes.