question for electrical engineers

[LCAM-01XA]

Oh, there probably ain't nothing wrong with it, just my E4OD was acting up weird and trackspeeder mentioned it could be the baro sensor but it's very likely I won't be able to identify it as the culprit until I replace it. I hate just throwing parts at something, so I figured since that truck rarely even gets driven I might as well try to do away with the baro sensor if I can, but from what you say it seems I'm stuck with the thing. Oh well..., hope I didn't mess up the PCM while playing with resistors today, would royally suck if I have to locate a "new" PCM for the darn thing.

By the way, 2.5V exactly, or it can tolerate a bit more or less? Cause mine actually reads 2.53V, not sure if that makes a difference tho.

 

[jpw]

2.53V good enough Freq MUCH more important! Key on engine off switch volt meter to hz and any where near sea level should be 158hz, maybe +- 1hz. if you are at altitude i can look up chart tomorrow( higher/ lower pressure=less hz). throttle position and manual lever position/curent gear are MAJOR E4OD inputs so much so that I often new (Ford OEM) MLP and connector repair pigtail for intermittent issues as 1st step before diagnosis.

 

[jpw]

if you are at altitude i can look up chart tomorrow( higher/ lower pressure=less hz)


should have said (higher altitude = lower Hz)

 

[LCAM-01XA]

Where do I measure the frequency, between the 2.5V wire and battery negative terminal? I'll see tomorrow what numbers I get... TPS and MLPS/TRS and their wiring all check out good, VSS on the other hand was questionable at best, will see now if the new one fixes the problem.

 

[LCAM-01XA]

Actually, if it ain't too much trouble, can ya copy-paste the altitude vs. frequency table in here? This way the info may help someone else in the future as well...

 

[jpw]

paste no work just google "ford baro sensor chart" and look for one w/ Hz

 

[Agnem]

That's pretty damn funny. The second hit in Google, is THIS thread with the previous posters quote as the hit.

http://fordfuelinjection.com/?p=32

Check out that link.

So what you have here then, is a 5 volt signal being passed through a crystal which is vibrating at a particular frequency based on altitude. The frequency is measured at the sense pin, and in all likelyhood the circuit that reads the sense pin is current sinked rather than current sourced. So what you would need to do is hook an ocsilloscope or frequency counter to the sense pin and ground, to read the frequency. Then built an astable multivibrator out of a 555 chip (http://en.wikipedia.org/wiki/555_timer_IC) sinking current for the sense circuit which you could then substitute for the presure sensor. An added bonus, would be a potentiometer in the cab for adjusting the frequency to tailor your shifts. Then again, we could just replace the E4OD with a ZF-5 which would be a heck of a lot better solution all around.

 

[LCAM-01XA]

Duh, completely forgot about FFI's website! Okay, so how do I build a current-sinking circuit with the 555 chip? Looking at the diagram for astable mode, it's a frequency generator with pin 3 being the output, but that looks like a current source circuit to me - how do I turn that into a current-sinking circuit and tie it into the "baro" wire from the truck harness? Also I assume the Vcc for the 555 chip would be my Vref from the baro sensor harness correct? Ground is ground obviously, and if I go with the potentiometer ("pot" just don't sound right these days, lol) idea that should probably be installed in place of R2 so it alters both the high times and the low times equally, correct?

The ZF5 swap, nope, don't think so - mechanically the slushbox actually works great (when electronics allow it to, lol) and I generally do not like sticks in small vehicles. That said if the E4OD goes within my lifetime, I would probably replace it with a hand-shaker of some sort, in the interest of less wiring in the truck, but hopefully that ain't something I should be worried about any time soon.

 

[typ4]

That's pretty damn funny. The second hit in Google, is THIS thread with the previous posters quote as the hit.

http://fordfuelinjection.com/?p=32

Check out that link.

So what you have here then, is a 5 volt signal being passed through a crystal which is vibrating at a particular frequency based on altitude. The frequency is measured at the sense pin, and in all likelyhood the circuit that reads the sense pin is current sinked rather than current sourced. So what you would need to do is hook an ocsilloscope or frequency counter to the sense pin and ground, to read the frequency. Then built an astable multivibrator out of a 555 chip (http://en.wikipedia.org/wiki/555_timer_IC) sinking current for the sense circuit which you could then substitute for the presure sensor. An added bonus, would be a potentiometer in the cab for adjusting the frequency to tailor your shifts. Then again, we could just replace the E4OD with a ZF-5 which would be a heck of a lot better solution all around.

And the knob on the ZF is bigger than the pot knob.