Conditions for Running the DTC

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

DTCs P0601, P0602, P0604, P0606, P1516, P2108, U0107 are not set.
DTCs P0120, P0220 and P2135 are not set at the same time, or DTCs P0120 and P0220 are not set at the same time.
The ignition switch is in the crank or the run position.
The ignition voltage is greater than 8.5 volts.
The TAC system is not in the battery saver mode.