SS S/C No Boost - Cobalt SS Network



Problems/Service/Maintenance Do you have problems with your new 2.0, 2.2, or 2.4L? What kind of service did you have done?

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Old 02-15-2017, 09:50 AM   #1
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SS S/C No Boost

My friend has an 07 SS S/C that doesn't make any boost. However, if you do the boost bypass mod, it builds to 12psi. I'm thinking either the solenoid or the actuator is bad. Any other ideas? I think he has a code for the throttle position sensor (gas pedal assembly) but I don't think that would cut boost.

Thanks in advance.
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Old 02-15-2017, 10:28 AM   #2
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Could be the solenoid or the actuator, or both. I just replaced both of mine not too long ago. Fixed my lack of boost.
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Old 02-15-2017, 10:31 AM   #3
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Originally Posted by chris88z24 View Post
My friend has an 07 SS S/C that doesn't make any boost. However, if you do the boost bypass mod, it builds to 12psi. I'm thinking either the solenoid or the actuator is bad. Any other ideas? I think he has a code for the throttle position sensor (gas pedal assembly) but I don't think that would cut boost.

Thanks in advance.

What do you mean when you say boost bypass mod? Are you disconnecting the solenoid or are you physically forcing the bypass valve shut?

If you are just disconnecting the solenoid, your bypass actuator seems to be working like it should. If this is the case it could either be your solenoid or it could be your ECM pulling boost because of your TPS problem. I threw a TPS code once and it was because water got into the throttle body plug connection. My TPS code caused my car to go into reduced power mode so it is definitely possible that the computer is pulling boost because of your TPS error.
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Old 02-15-2017, 12:31 PM   #4
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No more code, TPS was replaced along with the boost solenoid. I'm guessing using a screw to plug the line running to the actuator is how he got it to boost. So it has to be the actuator, or a hose not hooked up right.
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Old 02-15-2017, 06:08 PM   #5
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No more code, TPS was replaced along with the boost solenoid. I'm guessing using a screw to plug the line running to the actuator is how he got it to boost. So it has to be the actuator, or a hose not hooked up right.

If the solenoid or the ECM via the solenoid was limiting boost you could bypass this function by disconnecting the hose that goes from the actuator to the solenoid. You don't plug any lines. This leaves only that vacuum reference line which routs back to the intake snout of the supercharger. If when the actuator to solenoid line is disconnected and the manifold is able to achieve both vacuum and boost then your actuator is NOT the problem as that indicates it is working like it should. The actuator is in a normally closed position and a vacuum signal between the super charger rotors and the throttle body will cause the actuator to open the bypass valve. The solenoid connected to the actuator can also open up the bypass valve if the computer is commanding it to.
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Old 02-15-2017, 09:20 PM   #6
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It boosts if you unplug the line from the actuator to the solenoid. Maybe the replacement solenoid is bad, lol.
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Old 02-15-2017, 10:15 PM   #7
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It boosts if you unplug the line from the actuator to the solenoid. Maybe the replacement solenoid is bad, lol.
As far as I understand it, and I could be mistaken, the solenoid limits boost in it's activated state. Meaning, the only way a bad solenoid would limit boost was if it was stuck on for some reason. It seems to me like you ECM is limiting the boost for some reason.
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Old 02-16-2017, 11:09 PM   #8
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I think the solenoid commands the actuator to close when you floor it. He's got some weird wiring setup from when he replaced it that might be why. Who knows. I'd have to look at it in person to really figure it out.
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Old 02-17-2017, 08:01 AM   #9
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I think the solenoid commands the actuator to close when you floor it. He's got some weird wiring setup from when he replaced it that might be why. Who knows. I'd have to look at it in person to really figure it out.
If the solenoid commands the actuator to close then why does it only close when you disconnect the solenoid? Like I said the actuator is closed in its inactive state. When it is activated it opens.

I have base model setup with supercharger and we don't even us a bypass solenoid. The bottom nipple on the actuator is open to atmosphere.
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Old 02-26-2017, 11:44 AM   #10
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Alright, this thing is starting to **** me off, lol!

Replaced actuator and boost solenoid to no avail. I put the solenoid from my car on and it didn't do anything. All hoses are good, no leaks.

Again, when you unplug the hose going from the solenoid to the actuator and drive the car, it boosts 12 psi.

I'm at a loss, here.
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Old 02-26-2017, 01:23 PM   #11
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if the mechanical stuff is working (it is, verified by doing the boost bypass mod) and the solenoid is good (verified by swapping it) then the solenoid has to be getting energised somehow. now i havent been able to look at a diagram, but if its a ground controlled circuit (12v from fuse box to solenoid and ecm controls the ground side of the circuit) it could be a pinched wire grounding out. look at a diagram and check with a multi meter. it could also be the ecm commanding the solenoid on for some reason. with a scanner look for a data pid for the boost solenoid, see what the commanded state is.
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