Trying to understand INF codes (paperclip method for retrieving codes)

I went out to my '04 Prius to pull the codes via the paperclip method. What I got was good stuff with some head scratching stuff.

The ((!)) codes were 41, 49, 57
The ABS codes were 42
The Air Bag codes were 51, 53

Looking at a thread with the codes displayed It seems there were no codes for 51 or 53. Hopefully someone can chime in and show them.

41 seems to be Brake Actuator Assembly....Rear Increasing Pressure
42 Skid Control ECU....................................Solenoid Left Hand Malfunction
49 Skid Control ECU.....................................Rear Decreasing Pressure
Harness and Connector

I couldn't find explanations for codes 51 or 53 but I did see codes for 501 and 503 and 305.

501 Initialization of Linear Solenoid...............Linear Solenoid
503 Valve and Calibration Undone.................Valve offset learning undone

305 Foreign object is attached........................Left rear speed sensor
on tip of rear speed sensor Left Hand


Here is a link to the trouble code explanations:
Brake, ABS,VSC, (!) warning lights on | Toyota Prius Forum

About a year ago I had the brake accuator replaced with one from a junk Prius. I didn't have TechStream to bleed the brakes so I had to take it to a guy who is a Prius Whisperer and he did a good job. Recently my Prius began having Christmas tree light problems. I put it down as a bad HV battery thus I replaced the HV battery. I had bought Dr.Prius' app and it showed I had two cells going bad. Thus I figured that was the reason the Christmas tree lights appeared on my dash. I'm glad I got a new battery because it showed to me that the corrosion on the battery terminals could have been causing some voltage drop. Lots of green corrosion on the copper plates. Got the new battery put in and the same lights came back on. So I pulled the codes with the paperclip method and was wondering if the accutator was going bad or if I had some debris on one of the ABS sensors. Maybe one of you guys could guide me on a course of action.

BTW, I know a lot of you are shaking your heads at my reluctance to purchase TechStream but I have looked into it. I went to EBAY and it showed some cables that connect to the car and a lap top, yet I was wondering if the TechStream app comes with the cable or is it a stand alone purchase? The cost is anywhere from $30 to $70 so any info you can shed on that would be most helpful. Would you trust an EBAY version of TechStream or is there a better supplier?

Thanks.