Conditions for Running the DTC

WARNING: This page is about a different car, the 2004 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.

The ignition 1 voltage is more than 7 volts.
The TP 2 voltage is between 0.15-4.8 volts.
DTC P0221 runs continuously once the above conditions are met.