I don't think hitting PDC will just activate it. It needs to engage in Reverse before you turn it off/on. Won't work just in any other gear. It will work in D AFTER auto turning on when in R

Turn the key on, do not start the engine. Press the PDC button.

Put your ear by each sensor. If the sensor is operating you will hear a faint, fast click/ticking noise. If you don't hear the noise the sensor is not functioning.

Hell of alot easier to scan the system for errors.

lol

Most of the time the sensors themselves just explode. It's easier to walk around and listen than to whip out the equipment and such.

Actually...there's a MANUAL ACTIVATION/DEACTIVATION of PDC for those times when REVERSE isn't engaged but you desire parking aid help from the PDC sensors. This comes in handy when pulling forward into a tight parking location or spot that may have an obstruction that you want to pull close to (within the approx 2 ft range of the front PDC sensors), but not hit (lamp pole, parking barrier or wall, hedges, small car's bumper, etc). :)

And there's the automatic activation of PDC (which you explain in your 2nd sentence)...which is activated by engaging REVERSE:

Is it deactivated over a certain speed? I have pushed the button while driving and nothing happens.

Yes, it's deactivated when it drive and over a certain speed.

It can be manually activated and deactivated when sitting still by pressing the PDC button.

I also think it's easier to walk around and listen than it is to boot up a computer, connect a cable, navigate through programs. Takes 30 seconds to walk around the car listening to each sensor.

this ^ +1

all you really need to do is listen for a second or two for each sensor..you'll know if it has the clicking sound or not.

Yeah, after 20 mph, it will go out. I think you need to come to a stop first then turn it on. Then you can proceed forward.

I agree to hassle with INPA or GT1/DIS is harder. BMW Scanner is easy. I have it on a Dell 2100 micro laptop I leave running in the garage. Takes no time.