I agree. I don't see how placing the 12v+ to ground would do anything but short the battery. The 12v- is connected to the engine and frame and is for all practical purposes the same as the 12v- on the battery. Shorting the battery for 30seconds is, well, buying a new battery. It is a short in any terms. I can't see how this would clear anything in the PCM. I have an Associates degree in electronics and this defies all logic.