It there a write up for diagnosis of Power Booster failure/ABS light+step by step repair??

It looks likely, but before you spend 10+ hours doing contortions it's probably worth confirming with some simple tests.

C1251 is related to an out-of-spec electric current measurement on the pump. The assembly includes a current shunt resistor (on the ground side of the motor) and three sense wires back to the ECU (+ side of motor, between motor and shunt, - side of shunt) so the ECU can monitor how much current the motor draws. Extreme values will trigger this code. The steps to check are on pages DI-406 to DI-408.

C1252 is a simple time-out on pump control; the ECU was calling for the pump to run for more than 5 minutes and the pressure didn't become satisfactory. Test steps on pages DI-409 to DI-415.

C1256 goes with one of five possible surprises in the timing of pressure switch signals, such as low pressure indicated for 60 seconds straight, or low pressure and high pressure signaled simultaneously, etc. Test steps on pages DI-424 to DI-429.

You could certainly see all of these codes if the pump just isn't running at all, which it wouldn't if the pump itself is toast or if the wiring/relays/etc. powering it have a problem. A relay/wiring problem ought to also give you C1253, which you don't have. A problem on the ground side of the pump might not give a C1253.

All the step-by-steps (for C1251, C1252, and C1256) start with you unplugging the two connectors at the pump (these are connectors H5 and H6, at least in the 2001 wiring book) and connecting a stout 12 volt battery straight to the pump's BM1, BM2, GND1, and GND2 terminals just to see if the pump draws any current and does anything at all. (Ok, that's the second thing to check for C1256, but the first thing for C1251 and C1252). That seems like a perfectly sensible way to begin.

By the way, all three codes you're getting are supposed to sound the alarm buzzer according to the chart on DI-360, so if you're not hearing it, this is a secondary issue to getting the main problem fixed, but you might eventually want to check whether the prior owner unplugged the buzzer or something. It's clipped to the side of the brake ECU up above the driver's right ankle and it looks like the image I posted earlier.

All my page numbers are from the 2001 manuals, could be slightly different in your year (or online at techinfo).

-Chap

 

You can get the service manuals either in paper form or online at techinfo.toyota.com. I bought them on paper and the 2001 edition. The pages might be slightly different for 2002. I also don't remember for sure whether they use the same numbering online, as I haven't logged in there for a while, but all the same info is there and it's online so easy to search.

The organization of the manuals is like this: Volume 1 is the diagnosis information, codes, what they mean, how to eliminate the different possibilities, etc. All the page numbers I gave with DI- are in volume 1. Volume 2 has all the specific info on how to take stuff apart and put it together. If you're following the diagnostic steps in volume 1 and it says to change out the finnimbrun, volume 2 will have the steps for doing that.

The Electrical Wiring Diagram Manual is its own separate volume and very complete. There are circuit diagrams, physical layout diagrams of where things are in the car, a section at the back with drawings of all the different connectors (like H5 and H6 that I mentioned), what they're shaped like, what colors they are, and their pin numbering, and a cross reference to the physical layout page showing where you would find them.

Another volume is the New Car Features Manual, which is the one that explains how all the stuff in the car is supposed to work and why. The other volumes kind of assume you know that already and they start from there to diagnose why stuff isn't working. There's only a NCFM the year a new model comes out, so for Gen 1 you have to look for the one from 2001.

There's also a body repair manual, which is only about the kinds of repairs you need grinders and welders for. (All the body repairs you can do with wrenches and screwdrivers are in the regular volume 2.)

All should be online at techinfo.toyota.com. Paper copies can be ordered new from Helm, Inc., which has Toyota's distribution contract, but sometimes certain volumes can go out of print. Used copies might be on eBay.

-Chap

 

i found this for 64 bit.
How to run MINI VCI for TOYOTA TIS Techstream 8.x on Windows 7/8 64-bit? | OBD365.com Official Blog

 

So I got the ABS warning light and buzzer going off in my 2002 Prius (107,541 miles) last week, just before leaving for vacation. Man that buzzer is annoying! The light and buzzer comes on and then the brake pedal is soft but I can still brake. It then will go off (buzzer and light) sometimes and the brakes will function normal again. My local dealership says that my ABS pump motor with accumulator is bad, at a whopping $1944 just for the part. Current KBB on my car is $1200, so kind of rediculous to put that kind of money into the car. I'm assuming this is the same problem you had? And if so, could you link me to where you bought your part? And anyone know a reputable mechanic in the Houston area?

 

You found a dealer who's got a boat payment this month. List price for that entire assembly is only $1273, you can get it around $940 + shipping, that's brand new in a Toyota box.

If the problem is only in the pump subassembly and the old accumulator tank itself is in usable condition, the subassembly without the accumulator is more like $670 + s&h.

Labor to replace it will be high, it's hard to get to, though there is a report in another thread where someone successfully DIYed it in ~ 10 hours without having to disturb the A/C refrigerant lines.

Either price would be a lot to pay until you are sure a complete diagnosis has been done to prove the pump itself is bad and not the wiring, relays, or switches that are involved in the same circuit. It would be unfortunate to spend that kind of money and labor and then find out the real problem was something else. You, or your mechanic, should be starting with a careful list of the exact trouble codes from the brake computer and the diagnostic steps summarized in post #23 above, and the information in the service manual sections that post refers to.

Regards,
-Chap

 

I'm starting to think it may be a relay or switch issue rather that the pump because it doesn't do it all the time, just very random. I find if I turn the car off and then start it without pushing the brake, the buzzer and light will not go off. I plan to take it to another mechanic for a second opinion as I am not that mechanically inclined.

 

Where is the best place to purchase the literature with the step by step's showing the R&R procedures for this?

The codes I got were:
C1251 pump motor is locked / open circuit
C1252 hydro-booster pump motor malfunction
C1253 hydro-booster pump motor relay malfunction
C1256 accumulator low pressure malfunction
C1259 hv system regenerative malfunction
C1214 malfunction in hydraulic system

After clearing and a quick drive:
C1251 pump motor is locked / open circuit
C1252 hydro-booster pump motor malfunction
C1256 accumulator low pressure malfunction
C1214 malfunction in hydraulic system

After clearing and no drive:
C1251 pump motor is locked / open circuit
C1256 accumulator low pressure malfunction

I don't hear the pump running with the key on but I do here what sounds like a relay switching on and off.
When I took it out for the quick drive the traction control kept me from a continuous spin on the gravel but the brakes locked up on the pavement when I dynamited them. Also the brake pressure is all me, no power assist.
If I'm understanding what I've read here I'm pretty sure I've got my work cut out for me but it would be nice to have some written directions to speed up the process.
Any help will be followed up with profuse gratitude on my part. And if you live between Tacoma, WA and Portland, OR, I'd be happy to spring for dinner.
Thanks in advance.