Code P0122

When you say you tried pulling the cable from both ends? Do you mean the cable feels like it's binding up or is it the gas pedal that's not returning to its normal position? Also is there a stop screw on the side of the throttle body that can adjust the plates position? It's odd because usually a cable will stretch and be too long, therefore having slack in it, in this case your throttle cable is too tight. Is there an additional cable for the Cruise Control that's pulling on the throttle plates? Because honestly I can't see anything out of those pictures. Maybe if you can take 4 or 5 pictures during the day from different angles around the throttle body.
I mean now we have to figure out why the cable is so tight. Did this original problem happen suddenly or over time?
This is a cable I found from AutoZone, does this look like your cable (Pic 1)? You'll notice there is an adjustment screw towards the bottom of the cable.
Does it make a difference with the cruise cable off?

So there's no threaded adjustment on the throttle cable anywhere, with a nut on it? Not even down at the pedal? Something is holding that cable up, if you pull on the cable does it feel like it moves freely?
Have you followed the cable all the way down to the firewall, does it meet up with any other cables at any point or can you follow it all the way to the pedal and find no places where its kinked in a strange position or something?
I mean you've found the issue. All of those throttle body pics look the same to me, There has to be an adjustment on it somewhere. Cables don't just tighten up like that for no reason. I have been looking all over for diagrams and can't find much. Im doing some investigating and see if I can get a better diagram of where that cable runs too. Hopefully ill have more info tonight.
I do see that a lot of places sell a universal cable like you said. Not sure that will work for you though.
Can you disconnect the cable from the gas pedal?
One more thing, how does the throttle plates move with the cable disconnected, can you turn the plates freely, no binding or anything? Just pull the throttle linkage like the cable would be doing. Make sure that bearing in there isn't binding up.
So it seems other Malibu's have this same issue. They think it's an adjustment issue.

Okai, so after some more investigation from another source, this car supposedly does not have any adjustments for the cable. It's only the throttle cable and the cruise control cable. But we must be missing something here.
If you have the cable hooked up, without the cruise cable, it's still hanging the throttle plates open correct?
If so, is it possible to pull up on the gas pedal to allow for the little slack it needs? I mean we're talking about probably a 1/4" inch. Or is it possible that the spring on the throttle body is connected incorrectly? You said you cleaned the throttle bore, so it can't be carbon hanging the cable up.
The only thing I can think of at this point is the cable is maybe binding up inside its case,
I would say order a cable and replace it at this point just to see if that helps.
I'm running out of ideas here. Is the TPS holding it open? Have you had that off with the cable on and see if the plates are still open? Try that. We're missing something really simple here. Cables don't shrink,
Also try unhooking the cable from the gas pedal, and keeping it just hooked up to the throttle. See what that looks like.
I have never seen a TPS bind up and hang a cable up, but I suppose its possible. I'm not sure.
You're going to figure it one of these days and be kicking yourself, it has happened to me. But please let me know if you do find out what's going on. I really have to know at this point why those throttle plates are hanging open.

Is this bracket bent at all? You might want to take the whole throttle body right off the car and inspect every part.

Also, the springs that are supposed to pull the throttle closed are supposed to be wound around twice, I think there are 2 of them, if they're weak or not in the correct position, they might not be able to fully pull the throttle closed. With the cable connected can you pull the throttle closed by hand?

That bottom pic is yours, I don't think I see the spring hooked on there.

I just also read about the vacuum behind the throttle plates pulling them slightly open due to worn return springs, does this only happen when its running?

Awesome man, no you didn't waste my time, I knew we would find something crazy eventually. It almost always ends up being something simple like that. But think about what a forgotten nut lead to. I code for a TPS low input. But ha, you learned the basics of testing ECM circuits now. Plus, we're here to help to people. I'm glad you were able to find the issue without giving up and bringing it to a dealership. It has been a fun 2 weeks, lol. Anyway, good work. Have a nicer week. =)