> Hi All,
>
> This brings up some interesting points - MOPAR used to give a $100
>credit upon return of the old ECM. Would this still apply? It seems
>like having the new ECM flashed (necessary) would render the old ECM
>useless (at least to the individual). If one did keep the old ECM,
>couldn't it be swapped into the vehicle later (say, 5 years later, with
>the original ECM mileage numbers intact), thus giving one 5 years of
>driving without adding anything to the odometer? Then again, if it's a
>flash program, then why physically change ECMs at all? Wouldn't a flash
>program on the new ECM work the same as flashing the original ECM?
>After all, the "flash" IS just software... Just some things to ponder
>over...
>
> Russ Selkirk
Hmm random ponderings.... The ECM is just a simple computer. It dosn't
think on it's own. It only knows what to do from the program that is in
it's EEPROM. I would think the mileage is not stored on the main EEPROM,
it must be stored on a separate chip, maybe even outside the ECM
itself. Otherwise there would be a big stink over misreported mileage when
someone tried to trade in a vehicle or whatever (AKA/IOW rolling back the
odometer).
Changing ECMs changes the computer itself. Speed, design, etc. The
processors used on the ECM boxes only have a certain number of data lines,
and a certain number of IRQ lines (interrupt request lines). Every
function of the engine get's it's own IRQ, to determine which device or
task gets what priority owner processor time. It's much like your home
computer, but scaled down. It doesn't work exactly like I stated, I just
put it in simpler terms for easier understanding. On the GenIII, every
gauge connects to the computer. The charging system is connected to the
computer, the cruise control, the A/C climate control. There is even a
thermal sensor mounted under the battery that senses the temperature of the
battery so the computer can adjust the charging rate. And not only does
the computer have to run the engine, constantly adjusting injector timing,
adjusting the timing, it also has to crunch the OBDII program to make sure
all sensors stay in tolerance. That computer has to do a lot of things in
a very little amount of time. So if Chrysler got cheap on us and gave us
an "it'll do" computer, then we have problems. If anyone wants technical
info on the computer email me and I'll send you the url. It's good stuff.
I just dunno, not until someone starts writing down chip numbers, maybe I'm
barking up the wrong tree.
Mike
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