Chevrolet 2010 HHR Owner's Manual page 136

This is the position in which you can
operate the electrical accessories and to display some
instrument panel cluster warning and indicator lights.
The switch stays in this position when the engine is
running.
If you leave the key in the ACC/ACCESSORY or
ON/RUN position with the engine off, the battery could
be drained. You may not be able to start the vehicle if
the battery is allowed to drain for an extended period
of time.
This position starts the engine. When the
engine starts, release the key. The ignition switch will
return to ON/RUN for driving.
A warning tone will sound when the driver door is
opened, the ignition is in LOCK/OFF or ACC/
ACCESSORY and the key is in the ignition.
3-24
For vehicles with an automatic transmission, the
following procedure allows the ignition to be turned to
LOCK/OFF and ignition key to be removed in case of a
dead battery or low voltage battery.
1. Make sure the shift lever is in P (Park).
2. Remove the cover from the bottom of the steering
column.