A/C Diagnostic Code Translation Needed.

My 2002 Deville DTS AC system is not working correctly. It goes off and I get the service AC message. If I gun the motor enough to shift gears it will come back on and work for a while like it should. I have had it in to the dealer and It was a half pound low on refrigerant the first time. Second time it was down a half pound again, said there was a leak and fixed it. It didn't help.

I checked to see if it was throwing a code and got this code: PO532.
I looked that up and it says " A/C refrigerant Pressure Circuit Low Voltage".

Can anybody tell me what that means eaxactly ?
Thanks