Cleaned throttle body, now Engine Power Reduced message on

Tiny
AZDANNO04
  • MEMBER
  • 2008 CHEVROLET COBALT
  • 2.2L
  • 4 CYL
  • 2WD
  • MANUAL
  • 121,025 MILES
When I started car the idle is rough and got a message across the instrument panel stating Engine Power Reduced.
Thursday, December 2nd, 2021 AT 2:14 PM

8 Replies

Tiny
AL514
  • MECHANIC
  • 4,699 POSTS
Hello, the vehicle is going into what is called "Limp Mode" or Reduced Power mode because the engine computer (ECM) is detecting a fault, and it's commanding the TAC (throttle Actuator Control system) to only allow the engine to get up to a certain set speed, this is depending on the fault detected. You will have to have the engine computer scanned for diagnostic trouble codes. Your local parts store can most likely scan the vehicle for free. They will give you a code, usually it will be "P" followed by 4 numbers. Did this happen after you cleaned the throttle body? Did you force the throttle plates open by hand?
Also did you spray any solvents into the throttle body area? And/or was the intake Air boot put back on properly, there's no loose hose clamps or anything like that?

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing
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Thursday, December 2nd, 2021 AT 7:02 PM
Tiny
AZDANNO04
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  • 283 POSTS
I did remove the plate of the throttle body and used throttle body cleaner when cleaning the body.
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Friday, December 3rd, 2021 AT 2:33 PM
Tiny
AL514
  • MECHANIC
  • 4,699 POSTS
Is the check engine light on or been on since doing this? The ECM is in reduced power mode for a reason. You should have the ECM scanned for codes to see what's causing the issue. How did you remove the throttle plate? These systems are drive by wire systems. The ECM takes inputs from the sensor on the gas pedal (APP sensor, accelerator pedal position sensor) and uses those inputs for the fuel injectors pulse width and also moving the throttle plates. The throttle plates are controlled by a motor that is pulse width modulated and reverses the motor voltage to move the throttle plates in either direction. I'm posting the wiring diagram below to check the circuits, but since this happened while cleaning the throttle body, either some of the cleaner got into the throttle motor, or something happened to the motor while you were moving the plates around.
You can take the air boot back off, and with the key in the on position, engine not running, you should be able to see the throttle plates move with the gas pedal. But I don't think you're going to see that.
Checking the voltage to the throttle body is fairly easy, If you have a multimeter, you can back probe the connector at the throttle body. The grey wire is the 5-volt Reference feed wire, The purple and Dark Green wires are the Potentiometer signal wires going back to the ECM telling it how far open the throttle plates are. The Tan wire is the Ground. The brown and yellow wires control the motor for the throttle plates.
But get it scanned for codes, if there are no wiring issues or/and plates are not binding for some reason. You may have to replace the throttle body. AutoZone will scan the ECM for codes for free. Let us know what the code is, and we can give the code setting criteria and what exactly may have happened.
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Friday, December 3rd, 2021 AT 3:09 PM
Tiny
AZDANNO04
  • MEMBER
  • 283 POSTS
I purchased a new throttle body assembly. Is there anything I need to know before installing it?
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Sunday, December 5th, 2021 AT 2:47 AM
Tiny
AZDANNO04
  • MEMBER
  • 283 POSTS
The code was P0507.
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Sunday, December 5th, 2021 AT 2:48 AM
Tiny
AL514
  • MECHANIC
  • 4,699 POSTS
Okay, so p0507 is actually for "Idle speed 200 RPMs greater than desired idle speed". That could actually just be that the throttle plates are not closed enough. And allowing extra air threw, hence the high idle. It's not really that much higher really. You said you removed the throttle plate itself? Just the plate? Is it binding up or something due to not being installed correctly? Even the Throttle Position Sensor on the throttle body could be off by just a little bit. Is it adjustable on this throttle body?
If you decide to just change out the throttle body, there is a relearn procedure you're supposed to do with a scan tool, key on engine off. But you might be able to get away with just changing it out and erasing the codes. The idle relearn will take a few drive cycles for the ECM to relearn where the idle should be. So, it will just take longer without a scan tool, or it might just work out okay. Below are the torque specs too.
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Sunday, December 5th, 2021 AT 10:22 AM
Tiny
AUSTYN VANDERGRIFF
  • MEMBER
  • 1 POST
The plate hast to be put back in the right position or it will scrape the throttle body therefore giving you that code just went through it myself works fine no relearning no code scanner involved. I did not buy a new one, did not take it to a shop, pretty easy to do, but your conversation really helped me figure it out. Thanks
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Saturday, March 25th, 2023 AT 7:01 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
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Good to hear, please use 2CarPros anytime we are here to help.
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Sunday, March 26th, 2023 AT 12:42 PM

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