Need help. Brake, ABS and VSC lights are on and the prius makes high frequency noise

I have a 2008 Toyota Prius and a few days ago, the Break, ABS, VSC and the Exclamation lights came on. It has 154k miles on it. The first time they came on, the high frequency noise came on as well and faded away after about 10 seconds (the lights stayed on though). After driving about 2 days for short distances (because based on the forum discussions, I inferred that the breaks should still work), the noise comes on the moment I open the driver side door and stays on the whole time while driving.

I took it to Autozone for a free diagnostic and they gave me the codes as C1256 and C1391. I actually got the hybrid battery replaced a year ago (with a refurbished battery but still paid $1,100). After a month or so, someone stole the catalytic converter. It had been sitting on the drive way for 6 months and I recently got it put in. The car drove well for about 500 miles and then the current issue came up.

I am not sure if what could cause the current issue but just providing all the context for the knowledgeable people to provide the right suggestions.

Based on the previous discussions, any of the following could be causing the issue.

1. Break pad sensors - May be I need to replace the break pads
2. I might have to drain the break fluid as it might have built up some vacuum or air
3. Break sensor (not sure if this is the same as point 1 above)
4. Stroke sensor (again, not sure if this is the same as point 1 above)
5. Bearing hubs shot
6. Anti lock break pump

If the issue is with Options 4, 5, 6, the fix is going to be very costly.

I took it to an auto repair shop and they mentioned that the diagnostic fee is $175. When I showed them the codes from Autozone, they said they need to put my car under a powerful computer to get more details. And even if they put in a new anti-lock break pump (which could be anywhere from $400 for a used one to $1200 for a refurbished one from a company), they said it would cost me another $300 to program in the new part. The mechanic said the issue could be a minor wiring issue also but unless they run the diagnostic, they can't tell.

Ideally I would like to keep the car as it is good on mileage. But with these expenses, is it worth it? Is there an inexpensive way to diagnose and fix? The below thread talks about a cable and a bluetooth app on android (I have an iphone and so would need to borrow a friend's mobile). Being a novice at this, could I run the diagnostic myself and come to a fair understanding what the issue is or can I find a good mechanic who doesn't charge exorbitantly for the diagnostic?

Best diagnostic tools? | PriusChat

Please help. Please provide your suggestions on how do I approach this.

Thank you

 

Forgot to mention one other thing that I observed. When the care is in driving mode and if I am at a signal with my leg on the break pedal, the break pedal pushes my leg back and releases a little making the car move forward a little. I press on it hard to keep it in place.

 

Thank you for sharing the link to that post Bisco. I went through that link. So my only option is to replace the ABS pump based on the codes?

 

Sure, will take it to a shop to check the sub codes.