Peter,

The issue with the ntk is in the heater amp draw versus the gm sensor amp draw. A quote from the ford section on the iatn site =

Heater current outside limits:

< 0.30 amps or > 3 amps, (NTK)

< 0.45 amps or > 3 amps, (Bosch)

< 0.53 amps or > 3 ... Login to read more.