What year SC? It makes a difference.
Now assuming this is an early model (pre 93) Code 24 is telling you the ABS Computer thinks there ia a problem with the RF Inlet Solenoid valve in the Valve Body portion of the ABS Hydraulic Actuator. The only check to make is to pull the harness connector from the valve body (it is a 7 pin connector on the passenger side of the ABS Hydraulic Actuator) and measure resistance from Pin 1 to 7 on the connector on the unit side. If you read 5-8 Ohms you have a problem in the harness running back to the ABS Computer. If you measure outside that range you have a bad solenoisd valve and you are looking at a reman unit from our discount suppliers either Prior Reman or SIA.
Not sure abouty the hard pedal though. Are you getting either the Amber Anti Lock or Red Brake Light during operation?