So, you're on the prowl for a reprogrammed P28 ecu and you find some fella selling
one on Honda-tech. You pay the guy and he ships
you the P28. You receive it and there's no
part number sticker on the side of the ecu
casing - you scratch your head and think that's
a little odd
. You then go plug the ecu into your car all happy as hell, turn the car on and
rip down the street like your late to work
- but something's wrong - VTEC doesn't kick
on at all. So, you go rip around town a little
more just to make sure VTEC isn't working.
It never kicks on. You're not 100% sure but
you realize and lose faith in this ecu thinking
its NOT A P28. You go back home and plug
your stock ecu back
just to make sure VTEC works....and it does.
You then email the chap who sold you this
supposed chipped P28 ecu and give him a piece
of your mind; depending on how the seller
is he'll either take the ecu back, refund
you, or send you
the right ec, or bicker back & forth saying
it definitely is a P28...blah! blah! blah!
Well, here's the only article on the internet
(I assume) that will show you how to tell
a P28 from a non-P28 so this kind of scenerio
doesn't happen to you!
First off, this article is only covering these
OBD-1 civic and integra ECU's:
/ P06 / PR4 / P28 / P74 / P61 / P91
Normally, when an ecu hasn't
tampered with, a person can simply look at
of the ecu
for the factory
sticker as seen in [Fig.1]
and go off this as to what type of ecu it is.
Sometimes (and this is rare) a devious jackass
takes this sticker off or they
swap out the internals (such as putting in
a non-vtec main board into a VTEC casing) with
parts that are not what the specified
sticker is intended to be and pawn it off to
some poor unknowing soul....or a scenerio thereof.
What you want to do is remove the top cover
of your ecu and look for the board number which
is seen in [Fig.2]
(1720 for short)
the most widley used Honda OBD-1 ecu's around.
They're used in almost every SOHC & DOHC
VTEC & NON-VTEC OBD1 vehicles, with exception
to some LS and all GSR vehicles. These two boards are different in many ways but are similar when it
comes to specific transistors
which is the
There is a
third type of OBD-1 ecu
that Honda uses known as the 02D01980-1502
(1980 for short). This board is only
found in the OBD-1 P75
(LS) and all P72
(GSR) ecu's. See [Fig.3]
. The 1980 board is a totally different layout vs. the 11F0 & 1720 boards and is easily distinguishable if you compare the transistor location as I have in [Fig.4]
. We're going to ignore the 1980 board.
THE SECRET IS IN THE TRANSISTORS :
Now here's where you wanna pay close
" or "trans-lots
has a designated
which control the on & off switching of the
trans-lots which control auto tranny related
trans-lots look like - totally empty.
VTEC AUTO ecu
trans-lots would look like -all IC lots are filled.
A dead giveway for an OBD-1 DOHC VTEC B-series
ecu is the knock
as seen in [Fig.10]
You'll find the knock board on a US P30, P61,
you have it!
By having a trained eye, the transistors and knock sensor board can be a dead
distinguish a type of OBD-1 between a non-vtec/vtec and auto/5-speed ecu's no
matter what part number sticker is on the side of the ecu casing (or not).