ABS Pump issue (pump motor replaced)

Sorry for the quite long story here, but I'm feeling like I'm still in the middle of it.

2005 Prius with the ABS, VSC, brake light problem. All light up, the assisted brake was gone, plus the continuous beeping alarm noise.

Used a tester and identified the C1256 code - Accumulator Low Pressure. Also didn't hear the little pump engine working at all. Decided to take out the ABS assembly and see what could be the problem.

Identified that the ABS pump motor was gone, took it out of the assembly to see if it works, but it didn't turn at all, when hooked up to 12v, opened it up and found why it was seized up: full of rust and with two of the magnets detached from the case and stuck to the rotor. Also the rotor looked and smelled burned - didn't measure it but was garbage anyway.

Figured out that most probably the motor was causing the low pressure. From all available options for me, decided to buy a new motor (from China) and replace it in the assembly (a new pump was out of the question expensive, and used ones I really didn't trust by the looks of those available in my area, also read about others going through 3 used ones and still no fix).

I've put the whole ABS assembly back to the car, connected all lines very carefully - no leaks.

Did all that work myself, and only asked a mechanic-enthusiast neighbor for help with a compatible tester - that looked to be capable of air bleeding for Toyota. Turned out it was only sort of guiding us through manual air bleeding and didn't actually electronically air bleed the pump - or maybe we didn't explore all the available options of that software. Managed to air bleed the lines for each wheel (I hope), but I don't think we've got the air out of the pump itself, as it never got to that stage of pressing the pedal 30 times in 30 seconds that I saw other testers or Techstream required.

Now I still have codes for low pressure. But while doing the air bleeding the manual way, I saw that the pump motor used to crank and build pressure every time we took out the R8 (ABS MTR) Relay, the pump motor starts pumping and the errors and beeping goes away. Then if I press the pedal a few more times it cranks again and rebuilds it, but after a few presses the codes and beeping comes back. And if I repeat the relay take out process it builds pressure back again, and so on.
Also I noticed that the regular bussing of that little pump motor that we hear every time we open the driver door after it's been sitting for a while doesn't happen. I only hear the relay clicking, an no motor buzzing. An when I press the pedal I think I hear the solenoids working.

A few days ago I managed to get a Mini VCI and installed Techstream and get them properly working. Cleared codes and rebuilt pressure like I've described above (taking out the relay), the C1253 still lingers. As I'm preparing to do a complete ABS Pump air bleed, my question is: do I need to measure or replace relays to prepare for the air bleed?

 

I think I have committed a mistake here it's actually C1253 the error code that lingers.
So it's something to do with Hydro Booster Motor Relay.
I've read something called subcodes in techstream. I don't know how to get to them.

 

Thank you. Will do that. Didn't really know what that symbol was abaut.

 

C1253 Freeze Frame Data by Nirosorin posted Dec 10, 2025 at 12:46 PM

If this is answering some questions, please help me figure this out.

I've done an extensive research in the past few days and I find that the motor going out like this most times also kills the Power Resistor.
What do you all think?

I thought of using one of the other resistors (fuel pump or AC) and swapping it for the ABS pump a bit, just for diagnostic purposes.

 

Other details:

I swapped the relays with others from different functions (which physically fit the same connector and pins, and I also had two spares) - nothing changed. The pump motor does not buzz when opening the door after a short rest. So the problem starts when the door is opened. I hear the relay clank, it seems like it tries to spin, but nothing with the proper duration needed to build pressure.
However, if I start the car or leave it in READY mode, then open the hood, and, while it is still in READY, I remove relay R8, the pump starts (the characteristic buzzing), works for 2-3 seconds and builds pressure. The little pump motor starts running immediately when I pull the relay, before I even put it back, so keeps working with the relay in my hand. After I reinstall the relay and get back behind the wheel, the pump motor sounds correct every time it's needed, on the third or fourth consecutive brake press, just as it should and just as it worked when everything was fine. So the pedal press demands the pump to run and seems to work fine. True, the warning lights stay on, but the annoying beeping goes away.
Then, after turning the car OFF and ON again, if the car had the correct pressure before shutting it off, it won't throw errors immediately, but if I press the brake pedal a few times (so with the pump motor not starting), the low-pressure errors appear.
But it resumes working if I repeat the relay-pull trick.
From that point on, the car works perfectly. I did a test drive for 20 minutes and over 10 miles; the pressure does not drop, no more errors, the pump motor runs at the correct intervals, and the car drives and brakes properly, with assisted braking and apparently enough pressure (it does not seem to have air in the system). The ABS also kicks in when needed.