What can cause no rear brakes?

Here's the full scenario: 2007 Prius. Brake actuator has been running a lot, lately, coming on every five seconds for a few seconds. The other day, the Brake light, ABS, VSC, and orange exclamation point all came on. Seemed like a bad brake actuator. We had one in an older salvage vehicle, so did the full swap. Big job. Now I'm trying to bleed the brakes without Techstream. My DIAGKING Techstream is in the mail, but there's time pressure on this. I was able to bleed the front. Nice strong flow of fluid. For the rear I'm trying to use Mr. Electric's youtube method. Power off. Brake pedal engaged steady. Open bleeder... no fluid flow. Bleeder screws not clogged. If I start the car, normal ready mode, engine running, and apply the brakes, the front brakes engage and the rear brakes don't. My scan tool is a bluetooth with Torque Pro, so it's no help. I tried the pin 4 to pin 13 jumper. Seems like the codes clear at first but come right back, and still no rear brakes. On the plus side, the actuator no longer runs constantly. But I was hoping I could bleed everything and be good to go, maybe would need to have the linear valve calibrated, or, worst case, have a shop do a Techstream bleed job. I was thinking I must be in front brake failsafe mode, but when bleeding the front, I could hear the actuator pump running full time, and had fluid pumping out cyclically, automatically, with a powerful flow. I don't know enough about Priuses. Don't know what the possible explanations are for no rear brakes.

 

Update: I had forgotten to do the 8-plus rapid brake pedal presses after putting in the OBD2 jumper. When I did that, the ABS and VSC warning lights all cleared. Holding the brake pedal down with a wooden rod against the driver's seat, I was able to bleed the rear brakes. Only got an ounce or less of fluid each time I released and reengaged the pedal, or every other time. No steady flow happening. Brake pump would run briefly and a little fluid would flow. Once I'd gotten several ounces of fluid from each side, I restarted the car. The Brake, ABS, VSC and exclamation point all came back and there were front brakes but no rear brakes again. I assume those codes came back because of the bleeding. But using the OBD2 jumper again I cleared all those, and rear brakes were finally restored. Now everything seems normal. We've driven it a lot today and had no faults.

Question: I did this without Techstream. I'm wondering whether lingering, un-bled air bubbles in the actuator could become problematic later. If we've driven it 75 miles should we have gotten a fault by now if there's a problem? If it needed the linear valve calibrated, should we have gotten a fault by now?

 

Oh, oops. I assume you mean ABS or VSC might not work right, and I won't know until I need them, which could be a bad time to find out. Well, I'm excited to report that I just received my USB OBDII cable and Techstream software from DIAGKING, and it seems to be fully functional on my Windows 11 64-bit laptop. Now, if I can just get my daughter to come back to Vermont from Chicago, I can do the bleed properly. By the way, that cable is no longer available on Amazon. Had to order it direct for twice the price, but it's working, and I wasn't too confident about the alternatives currently available on Amazon.