ABS Quandry

Are you putting in used actuators? If so this makes diagnosing the issue much harder. A new actuator will have a warrantee that it will work for one year. It will also come with a new resistor to match the new actuator.

You can introduce a host of problems with a used actuator unit, to include fluid contamination etc. Have you bleed the brakes with the procedure in Techstream. Also did you calibrate the new actuator to the vehicle? When you replace the actuator there is a whole procedure for calibration and brake bleeding after its installation.

Having done this repair to our vehicle I was curious about if you had followed all the procedures for this repair and were still having problems.

Here is a link to a post discussing the code you described
C1253 DTC 136 Hydro-booster pump motor relay | PriusChat

Look at post 8

 

You can pick up a remanufactured unit now for about $600. Not cheap but much cheaper than a new one from Toyota, and not that much more expensive than a salvage yard unit.
the resistor is not absolutely necessary to make it function what it will do is change the sound that the pump makes when it runs.
I'm not sure about the calibration, I didn't do that when I change mine out and my brakes seem to work fine. I also did not change the resistor.
I got lucky and found a used one at a salvage yard that was in an actual running car and they were able to check there were no codes stored, and offered a return policy if I put it in and it didn't work. We did discover that you do not have to put in a specific part number accumulator pump. Toyota will tell you that only a particular one will work in your car. But the reality is the replacement accumulator pump that they put in all of the second gen cars has the same part number. Which means there can't be much or any variance between the three different part numbers that were used during the cars lifecycle 2004 to 2009. My suspicion is that there were three different suppliers for the pumps and that is why there are three different part numbers. The one that I put in my car was from an 09 I have an 08 and the part number on the pump does not match the one that came out of the car. And again mine seems to work fine, over 50,000 miles on it in the last year since I changed the pump.


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Below in the .pdf is a page from the Prius manual. Bullet point 1 is where they specify the procedures for the Brake Actuator replacement.
On some of the next pages they mention additional calibration procedures that are also required.

As mentioned some have completely ignored these procedures and had success using a salvaged part.

I was overly careful with this Brake Actuator replacement as it involved the brake system of the vehicle and my wife and kids often use this vehicle. I was taking absolutely no chances and followed the book on this replacement and the procedures the book specified after replacing the actuator.

The Toyota Prius Repair manual is the one that I use to guide my replacement activities as well as advice from a kind Toyota Technician who advised me on what they do when they replace these units.

I want to mention again I am overly careful when working on systems like brakes and also mention other have had success using salvaged brake actuators and completely ignoring the procedures in the manual.