Would a bad master cylinder throw a code?

2006 TRD offroad, automatic. I've been chasing a brake problem for about a week now, I've found a bad wheel bearing and replaced it, slightly better. Had a caliper that was dragging for a while that I replaced. The pedal is soft sometimes but other times its not. The truck is stopping pretty decent but the pedal isn't as good as it should be. No external leaks anywhere in the system, if the master was leaking internally would it throw a code? Trying to rule out the master without disconnecting the brake lines as my bleeders are super rusty and won't want to open.

 

When you replaced the caliper did the fluid in the reservoir all leak out?
If so there is a chance you have air in the master cylinder or ABS System.
I believe to bleed the ABS System is takes a scan tool.
Don’t hold me to that, as I (thankfully) haven’t had to do this yet on a 2nd Gen Tacoma.

 

Brake fluid should be clear, fluid that is cloudy, yellow or dark causes air and reduces stopping power.
A Turkey baster can be used to remove contaminated brake fluid.