Power Steering Problem

Here you go with descritions for the fault codes

C1523
-1    Battery Voltage High
-2    Battery Voltage Low
C1550
-0    Replace Electronic Control Unit (ECU)
-1    Electronic Control Unit (ECU) Internal Fault
-8    Electronic Control Unit (ECU) Internal Fault
-A    Electronic Control Unit (ECU) Fault - Random Access Memory (RAM)
-C    Replace Electronic Control Unit (ECU) - EEPROM Failure

I would suspect a battery or alternator failure. I think you need to monitor the voltage at the battery when the steering goes off. It should be 14v+. I suspect the C1550 is a result of C1523