so I bought this 2006 HHR from my sister in law car is running ok but I pulled codes and got the following I cant seem to figure out how to fix the P0916 code
going bald trying to figure where the gear shift position sensor is or one is even
on this vehicle

p0304
p0520
p0701
p0916
p0420

 

The gear position sensor is on the transmission, below the fuse box.

However, your main problem is most likely a wire frayed or burned or a fuse.

Check the ground location on the transmission near the oil filter housing. That could cause the P0916 and the P0520 and the P0701.

How is it running OK when it is misfiring? That could be the cause of the bad catalytic converter. P0420.

 

I have no Idea how this car is still running fine with all those codes you could feel it missing very little but it made it from chicago to dallas and now to El Paso with all those issues

 

The #1 cause of a fried catalytic converter is a misfire. P0420 means a fried converter 99% of the time.

What I meant was: it is NOT running OK, it is misfiring.

 

I get you and thanks for the info I will check out that ground Im pretty sure thats the issue the bottom of the car has some rust as well as the exhaust poor thing just needs some tlc and do you suggest about the misfire does it mean the whole coil pack has to be changed? or possible just one plug

 

Could be 100 different things from a hole in #4 cylinder to a loose plug.

 

Welcome to the site, pull the plugs and have a look, are they all the same colour?
The Codes can be related so let's check one thing at a time , the ground needs to be clean and tight. Let's start there.