[mackguy]

My understanding is that when you get the code, it should not be trying to run the compressor, and if the compressor's not running, I think the pressures won't mean much.

If you're sure the compressor's running when you have the code, then it would seem to indicate other problems in the system...

If you find the compressor actually isn't running, you'll need to get it running to add refrigerant. The FSM mentions bypassing the safety system in order to get the compressor to run for this step, or you can try disconnecting the battery for a bit to reset the system