Thank you everyone for your posts. Was that bet made on a 456M or 456? Is it a possibility that the 2 ECU versions output to be PWM on one model and DC voltage on the other? When cycling ignition switch on/off - there is a momentary voltage reading measuring across the ECU outputs. Waiting to borrow a handheld oscilloscope to further confirm. Yes, 100% duty condition was the intention. Hopefully didn't burn it out with 12V. Incidentally bench tested the old servotronic with 12V. It didn't react nor did i see any smoke, which led me to believe the unit was bad. How much resistance should be expected across the terminals on a solenoid like this? The servotronic (spoolvalve/TC) is a new unit. Harness from ECU output to spool valve Continuity test OK. I thought as a safety feature should PS ECU or power failure occur, that the spool valve would automatically set itself in a position of min assist (in case failure occurred @ 200kph.) If the opposite were true, then then this car's PS problem is not a software issue. Today the harness was unplugged/open circuit and had to move the car. There was a few moments when there was power assist! The pump is new. The rack works mechanically and isn't leaking externally. Is it possible an internal seal/rings is bad, allowing high pressure straight back into low pressure or some kind of blockage in the lines?