Hi Andrew. This is where you decide how much you trust your "Aftermarket tools". ?? It does sound most likely that you have a faulty Air bag ecu but I wouldn't be happy until I had plugged it in to a Tech 2 to Confirm that they all read the same results.

If the wiring is checked and found to be good then I would be "guin darn't scrapyard" for a used ecu to try for a comparison or looking on the internet for one.

Tony.