For the Generation 1 Prius NHW10 ( 1997 - 2000) the only scanner that works is the Factory issued S2000. Make sure that you get a serviceman with the correct scanner to diagnose your vehicle.
Kevin is the real expert in the area of the Prius Hybrid. In his latest post to the forum replicated here he explains how the battery management systems works.
Hi all on the forum,
It has been called into question "what is the S2000", what necessity is it to us, how can it be useful to us with regards an equalization charge.
The TECNO S2000 hand held scan tool is the Toyota main dealer diagnostic scan tool of Japan, during the 1990's(where and when the NHW10 was released), being different from that of the western world which was a Mastertech main dealer scan tool.
JPG photos of aspects of the S2000 can be seen in the file section under "TecnoS2000" .
When working with a Prius NHW10, the S2000 scan tool required an extra " prius special" S2000 flash card ( photoDSC00404. JPG) to access the Hybrid extra features of this car. Also if you look at the last photo DS00412.JPG in this file you will see the menu page that deals with equalization charging using this scan tool.
In the file section also, under "NHW10 scanner fault codes" you will find the Toyota technicians Hybrid system fault code sheets for this cars hybrid system, including the "code 2579.pdf" file on how to deal with the C2579 (red triangle of death) using the S2000 scan tool with the S2000 Prius flash card fitted.
In short, this was a quick fix solution to the long-term problem of the traction batteries gradual demise. Once there is a difference of over 1 Volt between the battery modules that the battery ECU fails to balance out, then the code C2579 is invoked and a fail-safe program is switched on to protect the battery (you may notice that less turtles appear after this happening) when the triangle comes on. The garage technician would then fit the S2000 scan tool, access the menu ( DS00412.JPG) and carry out an equalization charge. This is a quick boost charge to 100% capacity using the on board ICE and MG2, IRRESPECTIVE of how much heat it generates (see code2579.pdf file instructions) . During which the fail-safe program is also automatically switched back off. After which the technician would then carry out an adjustment to the SOC settings, also see photo DSC00412.JPG) to prevent any more likely hood of any over heating or imbalance until the next time. I suspect that if this "quick fix" did not work then, Yes, the battery would have been removed, and send back to Panasonic for rejuvenation. If you look at the "battery scan.doc" file you can see settings for "off board charging", and equalization of channel 1&2 charging that don't appear on the S2000 scan tool menu's.
So NO, I do not think that doing an S2000 equalization charge is better than a full strip down and rejuvenation, but it is a dam site quicker and safer to the technician. Plus it switches off the fail-safe protection programming that is part and parcel of the red triangle scenario, which may be affecting your economy if its on.
The trouble with doing rejuvenation to a battery pack on its own, is that you are stuck with the set adjusted SOC settings as is already set up in the ECU by the last Japanese technician whom accessed it, also if the Red triangle is still lit, then the protection program is still active. So you will not reap the full benefit of the rejuvenation. This is OK if your SOC setting is set high, but not if it is set at a low %setting.
In short, this is a highly software driven car, and whether you use the S2000 scan tool to do an equalization charge, or if you have the courage to do a full and more dangerous strip down and rejuvenation yourself, then there is still benefits to switching off the red triangle and adjusting the SOC readings if you can access an original S2000 scan tool with flash card, to do this. At the end of the day though, we should all do what ever it is that we can do, to keep these " what I think" are wonderful cars,
Going for as long as we can. By hook or by crook is nessessary, But please be safe.