Thought I would share my story since this seems to be a popular issue discussed here. I was getting p0121(throttle position sensor) codes on my '06 SS 2.4 with 194k miles.

I took the throttle body off and cleaned it up good, both sides and the blade too. Put it back on, started the car and it idled at 2800 RPM. I did research about a relearn procedure where you let it idle 3 mins, shut it off for 60 sec, then start and idle for 3 min. That did nothing for me and according to the bulletin the MAP pressure has to be above 5 for the relearn procedure and mine was under 5.

So I decided to just drive the car. Sometimes when driving if I pushed the clutch in the idle would go up to 3800/4000 and surge. After a couple days of driving it started to get better. After about 300 miles one day I started it and it acted completely normal. During this process I only got one pending code for a high idle and I erased it and it never came back.

So if you have high idle issues I'd recommend driving it for awhile before doing anything drastic. The problem will probably fix itself after some drive cycles.

 

Yep, I noticed the same thing. I have a 2007 Ion with the 2.4 - auto trans. After cleaning the TB the idle was really high. I did the "relearn" sitting at an idle for 3 mins - no change. So I drove the car until it went away. It's really hard on the automatic transmission since it slams into gear and wants to go - the brakes are constantly squealing as you try to slow the car down. You try little tricks like put the car in reverse first, let the idle settle and then shift into drive - so it does not slam into gear so hard. About a week to 10 days later - it's back to normal - very annoying.

Same basic thing happened in my 2006 GMC envoy, not quite as bad but same deal. I hate cleaning the TB, but it has to be done from time to time.

 

Hello all, I have a 2010 Chevy Cobalt. I have the check engine light on and I suspect my throttle position sensor is the problem. Unfortunately I dont know where it is to test or take it out so I can try starting the car and seeing if the CEL goes away. Does anyone know where it is. I know its somewhere under the hood but beyond that I am not sure. I have tried looking online but the closest I have found is a 2007 model so far.

 

I believe the throttle position sensor is built into the throttle body. You can try cleaning it but don't move/force the blade open.

 

This is my set up i cant seem to figured it out well i talk to zzp apparently i suppose to use the cobalt 2.4 map sensor and i was trying to used the lsj. Here is my tb wiring

 

Solution: needed the 2 bar map sensor and it goes on manifold. It rev at 1000-1200 it sounds good too thank you guys!!!!

 

I'm having the same issue just slightly different. I was having less responsive throttle response so I decided to buy a new tb instead to fix the problem and eliminated any issues. Boy was I dumb. My car drives worse now than when I had the original tb in. My car was reving to almost 3k rpm in park tonight. i'm beyond frustrated with it.. So is the general consensus that in order for this type of thing to go away is just drive the **** out of the car until it relearns itself? And since i'm auto like you i'm getting the same harsh shift. The other issue is that i'm tuned also so i'm afraid my engine is going to go lean and blow up. If any current members see this please let me know what I should do. I already did relearn and it did nothing. I'm feeling like giving up. I just spent like 3k in suspension and new fuel lines for this car and will be going supercharged next spring. right now how angry I am I feel like just selling this car because i'm beyond frustrated now.

 

It's been a long time since I last cleaned a TB on these cars, but I ended up having to driving for a week to get the computer to recognize that there wasn't carbon on the plate. You might be able to tune it back with a commanded throttle position % but I'm not sure how true that is either as I never did that.