Skid Control ECU vs. ABS Pump (Brake actuator)? C1252, C1256, and C1391

So this seems like a story where the skid ECU is giving you three codes that indicate an impaired ability to pump up and maintain hydraulic pressure, and the question is, are those codes for real, or are they being reported spuriously just because the ECU is faulty?

That's not an unreasonable question to pin down before replacing stuff, but in this case, you've also got

so if the ECU is somehow delusional and only imagining the hydraulic pressure is low, it has managed to persuade the physical brake pedal to join in its delusion. If there are journals of car psychology, that could be a groundbreaking case study.

 

Do a quick check on the 12v battery and jump points. Some here believe the pump can or will act up around lower voltages.

 

All appearances here are that the ECU is perfectly healthy and doing exactly what it is supposed to be doing by telling you about your hydraulic pump problem.

Replacing the ECU would be shooting the messenger. Replacing the actuator assembly would be solving the problem.

The ECU is not attached to the actuator in Gen 2. (It is in Gen 3. But then in Gen 3, the pump is off in a different assembly.)

 

Maybe @JC91006 can chime in on this job.

Since the labor cost is below average (relatively speaking), you might consider the Dorman product with a 'Lifetime Warranty".

No sense in dropping a used actuator in and it failing prematurely, or the mechanic telling you the job was correctly done and claiming the used part that was supplied/installed is bad, leaving you in a having to repay to play situation again.

Many have replaced just the actuator without the brake resistor assembly, they may come as a matched pair :

Doubtful the ecu is the problem, the brake/skid control ecu is near the brake pedal (heat sinked with a gray plastic buzzer):

 

I suspect the actuator you put in is a bad part or something got loose. I would check your work again and make sure all the brake lines are tightly secured.

When I try to start the car with the actuator removed (no pressure from the brake pedal), I would hear the beeping sound you're describing.

I would be very careful buying used actuators online, many people may be selling off the bad units they remove, to recuperate their cost on the part. Buyer beware

 

Here is the workup for DTC C1252 and C1253 : https://share.qclt.com/%E4%B8%B0%E7%94%B0%E6%99%AE%E7%91%9E%E6%96%AF%E5%8E%9F%E5%8E%82%E8%8B%B1%E6%96%87%E6%89%8B%E5%86%8Cpdf%E6%A0%BC%E5%BC%8F/Repair%20Manual/04pruisr/05/21avn/cic12525.pdf

Here is the workup for DTC C1256 : https://share.qclt.com/%E4%B8%B0%E7%94%B0%E6%99%AE%E7%91%9E%E6%96%AF%E5%8E%9F%E5%8E%82%E8%8B%B1%E6%96%87%E6%89%8B%E5%86%8Cpdf%E6%A0%BC%E5%BC%8F/Repair%20Manual/04pruisr/05/21avn/cic12565.pdf

Here is the workup for DTC C1391 : https://share.qclt.com/%E4%B8%B0%E7%94%B0%E6%99%AE%E7%91%9E%E6%96%AF%E5%8E%9F%E5%8E%82%E8%8B%B1%E6%96%87%E6%89%8B%E5%86%8Cpdf%E6%A0%BC%E5%BC%8F/Repair%20Manual/04pruisr/05/21avn/cic13916.pdf

 

I replaced the actuator for our 2008 Prius. Not wanting to play around with this multiple times and since it was a component on the brake system I bought a new unit form Toyota.
Here is the invoice

Order Content
Part Number

44500-47141

Actuator Assembly

$1,134.95

1

$1,134.95

Subtotal:

$1,134.95

This is the part number for the upgraded actuator which will not have the same problems as the one you are replacing!
My experience- bought a used unit on ebay and sent it back as soon as I opened the box and saw the shape the unit was in got a full refund and went with the brand new Toyota OEM improved unit.

If you are fixing this car to flip you are probably going to go the cheapest route.