Hello Bert,
The MIP0221 is an interesting component. It has quite of bit logic that drives the control (gate) pin of the power MOSFET connected to the drain and source pins. I will caution you to use lower Tracker voltages when testing as power MOSFET devices can be sensitive to reverse (negative) voltages. Keep the voltage below 5V and you should be okay.
It is difficult to generalize what a good or bad signature will look like so it is best to look at the signatures of several good devices to establish a baseline of good information. This will help you decide when you have a bad one. As with most semiconductor components, always suspect it is bad if you see any resistive change in the signatures.