idt's right - One of your ground wires, more specifically, the parking break ground wire, is loose and/or not connected properly. Go through all your wiring connections again and make sure none popped out.
If you were trying to do the hardware bypass you might have missed a step. If I recall correctly, you need to move a pin on the harness and then wire that wire up with the ground wire. Since your question didn't mention how you installed your unit, I'm only assuming and this could not pertain to you whatsoever.