PSU sensor is not detected

Hello,

I've got a weird problem, the PSU sensor isn't listed.

That cause the CPU to run at 1,6Ghz constantly..! What ever the charge is..

Is there anything I could do, except buying a new PSU..

PRAM & SMC reset already done without succes.

I've changed the PSU with a old one (faulty but working), that cause the PSU sensor to show and CPU goes well.

Since I couldn't change CPU freq from OS X system, I need hardware solution(s).

Thank you.