The tire pressure measurements are derived from strain gages on the rims of the tires. The signals pass through a dedicated signal conditioner [DSC] in the midbody, and a multiplexer/demultiplexer [MDM], then a pulse code modulation master unit [PCMMU].
There is no cockpit readout for these measurements. The folks on the ground watch them, and if they get way out of range, a message pops up on the shuttle CRTs (which it did in this case).