Chevy HHR Jump Start
If you need to jump start your HHR the first place to look is under the hood. You will notice that there is no battery for it is located in the trunk to the right of the spare tire. You may find the the rear hatch will not open as well. This is because the battery charge is too low to actuate the hatche’s electric switch.
With the hood open, look to the right for what looks like a battery box. It is the relay and fuse cover. On the side of this is a red plastic toggle type cover that pops open to expose the positive jumper terminal for jump starting the HHR. Attach the red jumper cable to this terminal and the black jumper cable to a shock-strut mounting bolt nut located near the fender. Remember positive to positive and negative to negative.
Here is a YouTube video showing the procedure.