This message from Kevin in the Yahoo Mk1 Prius Forum
I own a Prius Mk1 and have done a considerable amount of
research on the scanning of this car. Despite the fact that it has a
> > > standard 16 pin OBD connector, it is one of the first few cars to use
> > > the 16 pin connector BEFORE it was adopted as any sort of standard.
> > > The standard of "OBD-11" only applied as compulsory in the USA from
> > > 1995 anyway, and car manufacturers only had to comply with OBD-11 if
> > > they wished to sell there cars in the USA from 1995. Toyota did not
> > > wish to sell their Prius Mk1 outside of Japan and the 1995 OBD-11
> > > protocols around at the time did not suit their needs, as they were
> > > inadequate for this car. I can reveal that the car is using "Toyota M-
> > > OBD", Toyota multiplex onboard diagnostics acording to people who
> > > specalise in toyota OBD.
> > >
> > > In the 16 pin connector (correctly known as the J1962 socket) the
> > > pins are as follows :-
> > > pin 16 = battery
> > > pin 4 = ground
> > > pin 13= test pin
> > > pins 6,7,9,14 are communication pins
> > >
> > > the Prius Mk1 uses a ECU for each of ,the engine, the ABS, the
> > > airbag, the Hybrid running gear and finally the Hybrid battery.
> > >
> > > Toyota themselves use a "Techmaster scantool" with an "S2000"
> > > cartridge adaptor, with software that they wrote themselves just for
> > > this car, only available to Toyota maindealers in Japan. The software
> > > itself uses "keyword protocols", (that's code words to you and me),
> > > using ALDL speeds of communication ( Assembly Line Diagnostic Link),
> > > now known communally as OBD-1 speeds of communication, first used
> > > commonally by General motors in the mid 1980's.
> > >
> > > The problem with getting a scan tool to handle the prius Mk1 is, that
> > > the scan tool needs to handle "Toyota M-OBD" keyword protacols, It
> > > also deeds to have a "J1962 connector" with the correct pin
> > > configuration. .
> > >
> > > All OBD-1 and OBD-11 dedicatated scantools will not work on this
> > > car !!!!!!
> > > I know, I have tried several of them that are on the market. Some of
> > > them costing several thousand of pounds.
> > > There are some of the more expensive ones that do the Prius MK11(
> > > which is OBD-11 compliant using more common keyword protocols) and
> > > Prius Mk111&1V using OBD-11 "CAN" (continuose area network protocols).
> > >
> > > So "what's to do then"?
> > >
> > > The only "After market" scan tools that are known to read the OBD's
> > > of the Prius Mk1 cars are the "Carman" scan tools range made by
> > > Nextech. The Carman A200( now discontinued) , the carman scan lite and
> > > the Carman VG. The scantools also have to have the september 2007
> > > software update to get the best results as well. The carman scan lite
> > > is £1500 ($3000) retail.
> > >
> > > I own a Carman scan lite, and the scan tool Is "brilliant", as it
> > > leaves no stone unturned, you can get all the information from the
> > > car that you need on any aspect.
> > >
> > > All 20 of Prs of modules in the Hybrid battery are shown including
> > > voltages, Ohms, temp of each Pr. Also the overall max and min
> > > voltages and temperatures of the monitoring system and exact % of
> > > overall charge as well as information on every sensor on the whole
> > > car.
> > > it will give you all the trouble codes on each of the ECU's and
> > > enable you to reset them as well.
> > >
> > > The only down side to the Carman scan tools are that they do not "
> > > flash" the ECU's, that is to say that, as of yet, the software dose
> > > not turn the " balance charge request" from "OFF" to "ON" and back
> > > again, even though you can see it on the scan.
> > >
> > > One of the problems with these cars is that the cells in the Hybrid
> > > battery are an early type of "high capacity" NM-Hi, and over time
> > > they may suffer from the " battery memory affect", problem similar
> > > to NI-CAD cells, and they discharge more rapidly if left unused for
> > > any length of time as well. Toyota thought to overcome this problem
> > > by using their scantool to do the "balance charge request"
> > > manouver ,by using the cars own charging system,( a full
> > > overall/across the board 110% charge) to rejuvenate the whole Battery
> > > in one go, if this failed they would fit a free RE-CON battery
> > > instead, all though this was rare. So sadly, we "outside of Japan"
> > > owners can only strip the Hybrid Battery down ( be careful they are
> > > 315 DC volts when fully charged, from first to last terminal,
> > > according to my carman scantool info, electricians tools and gloves
> > > required). You then have to rejuvenate each module, one at a time,
> > > replacing any failed ones, and finally rebuild the battery again
> > > using as evenly as balanced pairs as you can. The Carman scan lite
> > > can help you monitor this Process but " If only" it cannot do the
> > > balance charge manouver as of yet as I have said. Some cars go on and
> > > on, without problems ( 100,000 miles +) with the battery, some have
> > > stripped the battery down and replaced a " too good" a module, to
> > > achieve a balance. So until hopefully, Carman sortout a "balance
> > > charge manouver" setting on thier scan tool, in one of their future
> > > software updates, we will still have to do this by hand. Other wise
> > > the carman scan tools covers everything else and is unique.
> > >
