[Diy_efi] Jeep/Chrysler ECM reprogramming

[Andy Harvilla]

Hello there,

I've been frequenting the DIY PROM board over at Thirdgen.org for a
while (member blue86iroc), working on tuning my '86 IROC.  I'm still a
newbie with this stuff (an eternal newbie, haha), but things are sorta
kinda coming along.  I'd like to say hello and promise I won't be too
much of a nuisance ;-)

My other car is a '98 Jeep Cherokee, and I've been wondering if it's
possible to reprogram the ECM like my Camaro.  I know there's huge
difference between OBD-I and OBD-II, but the Power Programmer and
Superchips guys certainly know how to change the code.  There's hardly
any information on this stuff... most of what I've found regards
dealer reprogramming, which surely isn't what I'm looking for.  I'd be
tickled just to get the hexidecimal calibration data on my PC.

Whilst searching for Jeep info, I came across numerous technical
bulletins for reprogramming the ECM from the dealer.  For example, one
of them dealt with a code change to reduce spark knock.  Chrysler
listed two required updates, an "Authorized Service Update" and an
"Authorized Modification."  Both of the part numbers match updates for
other Chrysler vehicles, everything from Neons to Vipers, but they
covered other fixes.  The impression I get is that these are kinda
like cumulative updates for a wide range of applications.  Obviously
you aren't swapping Neon timing tables for Viper data, so how does
this system work?  Does the programming device read the vehicle type
from the ECM and tell the technician which updates are valid?  This
isn't really pertinent to my initial question, but a curiosity
nonetheless.  Maybe someone who's done this before has an idea of
what's really going on.

I also thought about swapping over to a GM ECM, since there's a large
user base and I'm already familiar with it.  Unfortunately, I don't
think the state inspection program would appreciate me switching from
OBD-II to I, despite the fact that I'd probably have fewer emissions
and better fuel economy.  Hmm...

Andy