Chris,
If you are unable to bench bleed the master cylinder and it isn't drawing fluid, that certainly does sound bad. However, the code you provided is specific to the YAW/G sensor signal.
Take a look at the first three pics for a clear description of the code. Additionally, the last two pics are diagnostics. The description (pic 3) indicates voltage references to the HECU. You may want to confirm those are correct.
As far as the master cylinder and based on what you are experiencing, I would replace it.
Take a look through the attachments below and let me know if they help.
Take care,
Joe
See pics below.
Images (Click to make bigger)
Wednesday, March 2nd, 2022 AT 6:03 PM