PassKey III

Apparently, most GM cars have PassKey III after 1996, which uses an RFID... odd, considering my '99 Bonneville has a resistor pellet (and I guess is PassKey II). This makes some sense, as the '04 Grand Prix keys are marked PK3.

However, both the '98 Sunfire and the '97 Tahoe are both well optioned, however, both use a metal key which cannot possibly have a RFID in it. I can believe the Tahoe might have had PassKey III bypassed... but the Sunfire has spent most of its life in out family... I can't imagine that it was bypassed when the car was less than 6 years old... in fact, I find it hard to believe both vehicles might have been bypassed.

Is there some sort of easy way that PassKey III can be "trained" to use a non-RFID key? Anyone know what might be going on here?

I ask because the Sunfire has a parasitic battery drain, and I may have to replace the BCM... which seems to be related to the PassKey system... and I'd hate to find out my "new" BCM needs a proper PassKey III key.