Oldblue

The lobotomy is really a simple reset of the HHR’s computers, disconnect the ground terminal at the battery for 30 minutes.
It’s always been my practice to avoid shocks or sparks, or frying electrical components to disconnect the battery while working on the engine or the fuel system, even the wheel hubs in the ABS equipped.
You do not need to disconnect the positive cable unless you’re changing battery’s , in which case be very careful to ensure the positive cable doesn’t touch the negative cable or the body, this can cause issues in the RAP system, I fried the radio in my 2007 last summer.

Bonez

You cant manually move the throttle plate to clean ( can damage it ) so it has to be removed to clean the "inside" aka back side... get a soft brush to scrub it, you don't want to use anything harsh.

Bonez

Being these HHRs are drive by wire, would dirty contacts cause that as well in the pedal? Use some contact cleaner maybe?

Oldblue

Can do, but unlikely it will help. The last TCM update was in 2008, it helped my ‘07 , but it’s the same programme in my ‘11.
dirty throttle body
dirty engine oil
dirty MAF sensor
vacuum leak, in my case the EVAP valve was leaking, only set a code every other fill up.

skysailor

I did manage to clean both sides of the throttle plate by having someone sit inside the car with the key turned to ON and depressing the accelerator pedal. That made the throttle move to full open and allowed me to spray cleaner on it enough to clean it very well. Note that it did not start easily the first time after doing this due to the flooding with cleaning fluid. :)