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High idle and not disengaging from park after cleaning throttle body.

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On my 2009 chevy suburban, I had a p0121 code a few months ago, and I cleared it, and it hasn't come back. I found that a dirty throttle body could cause that code, so today I got some throttle body cleaner, took the throttle body out, and cleaned it. It was pretty dirty and I got a bunch of black gunk out. I did move the throttle valve as I read online somewhere that moving it slowly without forcing it is fine. I noticed a high idle of 1.5k rpm, and drove it 500ish feet to the house. When stopped, the idle kept going up to 3000 rpm, and I turned the engine off. The check engine light was on, and I got the codes

  • P0122 - Throttle position switch A/accelerator pedal position switch A low input
  • P0222 - Throttle position sensor B/accelerator pedal position Sensor B low input
  • P0223 - Throttle position sensor B/accelerator pedal position sensor B high input
  • P0507 - Idle speed control system rpm higher than expected.

On my Bluetooth scan tool, it said the throttle position was at 26% when idling, and 85% with the car off and the pedal fully pressed.


I found a forum post saying that the throttle position needed to be relearned and to start the car and let idle for 3 minutes, stop, let idle for 3 minutes again, then drive for 10 miles. The car still idled at 3000 rpm during that time.


I did that, and when I put the car into drive, nothing happened, and the car would not go forward. I did accidentally drop the cover for the air filter that had the MAF sensor. With the MAF sensor unplugged, the idle jumped around and was at 1.5k, but after 20 seconds, it went back to 3k.


What could be the problem? Did I somehow damage the throttle body? Is there anything I can do to fix it? Im going to leave the battery disconnected overnight to see if that changes anything.






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This morning, I plugged in the battery, cleared the codes, and started. At first the idle was at 2k rpm, then slowly down to 1k as I was doing the relearn procedure. Seems like it was fixed! However, I then took it driving for 20 minutes getting up to 55 mph, and 5 mins before my house, I put it in park to see how the idle was, and it went back up to 3k. When driving, it accelerated up to 25 mph without pressing the pedal, and letting go of the pedal at higher speeds did not slow the car much. Luckily, I wasn't blocking traffic. No amount of unplugging the battery, clearing codes, restarting the car, and letting it idle for a bit would bring it back down. It also didn't engage drive. For now, I left it with the battery unplugged and will try again later when the car cools off.


The only codes that came back were the idle too high code, and 2 codes about alternator failure 😬




Edited by 2009_Suburban
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I watched this video, and it said a solution was to reset the idle learn

I did some research and bought this scanner after reading several reports that it works to reset idle learn on chevys.



Is it possible I damaged the throttle body, and I need a new one?

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Usually you need a better scan tool that can do a throttle relearn on it.


You can also try removing both cables from the battery, then touching the positive and negative cables together for 10 seconds and then hooking up the cables again. That usually resets the memory.

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The scanner (Launch CRP-129E) came in the mail today, and I was able to do the throttle body relearn. Once I did it, the car idled at 5-600rpm, seemingly lower than before this mess happened. I did the idle for three minutes thing and took it for a test drive. The throttle seemed slightly laggy, but it will probably get better when the car gets used to it. Did cleaning the throttle really allow that much more air in so it idles at 3k rpm, or did I misalign something when moving the throttle valve?


The scanner was kinda hard to use, but for people in the future with this problem, here is what I did:

1. Charged the scanner for awhile because it wouldn't turn on.

2. Set it up and connect to wifi (the manual covers this)

3. Go to upgrade and download the packages that say electronic throttle relearn and GM.

4. Press reset, and press ELEC. Throttle RLERN.

5. It will then ask you a bunch of stuff about your car. If there are things it asks that you do not know, just pick anything. For example, it asked if I had manual or automatic HVAC. Idk what this means.

6. Then there are three options related to the throttle, click idle learn reset.

7. At the bottom click reset.

8. This is where I got confused. There was no loading icon, no popup that said that it was reset or anything like in this video, just a value in a table that said reset. But apparently, once you press that button it resets the idle learn.


If that specific scanner is not available, they CRP-129X might also work, or just search Amazon for "throttle reset scanner" or "idle learn reset", and look at the reviews. Also, make sure it says returns accepted as other than the idle learn reset, it doesn't seem much more useful than a $20 ELM 327 scanner with the phone app.


Moral of the story: Don't clean your throttle body unless you have the $300 scan tool.

Edited by 2009_Suburban
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You knocked it out of calibration when you cleaned it.  I have always disconnected the plug from the TBs and then taken them off the intake and cleaned them, moving the plate at will to clean it and never had to do a relearn.  TB % at idle ought to be 3% to 7% or so.  The older and dirtier, the higher the percentage.  The o-ring is reusable but ought to be replaced if it gets knicked or hardens, etc.

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The best and easiest way to clean a throttlebody is to with engine off remove air intake tube at throttlebody and have wife  or friend turn on ign. no starting and have operator press throttle wide open, then spray TB cleaner inside wait a little bit and use a rag to clean the surfaces. Have operator release throttle and shutoff Ign. replace ducting and start engine, no codes or high idle.

This has worked for me flawlessly.

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