Conditions for Running the DTC

WARNING: This page is about a different car, the 2007 Chevrolet Cobalt. However, it is still accessible from the selected car via links, so may be relevant.

The ignition is ON.
DTCs P0120, P0220, P0641, or P0651 are not set.
The ignition voltage is greater than 5.23 volts.
DTC P2135 runs continuously when the above conditions are met.