Recently bought this car and the npp’s were stuck in loud mode. Checked the fuse and it was bad so assuming that was the only issue I went ahead and ordered the mild to wild kit…Hooked it up and still nothing. At that point I assumed the solenoid in the bumper was bad so I just replaced it and still nothing, what the heck? I guess my next step would be to check for vaccum at the solenoid but I don’t have a kit to check it…Any other ideas or things I could check?! Thanks

You don't need a kit to check if there is vacuum at the solenoid. You won't be able to measure vacuum, but you can pop the hose off and see if it sucks. You probably have a vacuum leak or a wiring issue to the solenoid.

Well yea true… so if I do that and there is no vaccum there, and I assume there won’t be, then what? I don’t know what to check at that point.

Then you would check the line going all the way up to the intake manifold.

What car??

Does the vaccum line connect to the back of the intake?
2012 Grand Sport

Yes. There is a small accumulator tank in the rear as well, check all hoses and work your way towards the front.

yep it’s connected… what the hell

That doesn't mean there isn't a leak somewhere. Or you could have sticking valve on the mufflers. Could also be an electrical issue.

Here is a thread that has some good information: https://www.corvetteforum.com/forums...schematic.html

I would also check the physical mechanism in the mufflers and make sure that they can actually move. Possible that they could have not moved in so long that they are stuck.

Also, check to see if the hoses are hooked up to the muffler actuators as well. Some people have disabled the NPP by disconnecting the hoses to the vacuum actuators. Or its possible that if work was done on the car and the exhaust was removed, they may have forgotten to plug the hoses to the muffler actuators back. Been a while since I removed my exhaust but I seem to remember there were hoses that drop down from behind the rear bumper.

It's likely something simple.

I checked the valves on the mufflers and both move easily. An electrical issue is a possibility because when I was cleaning the engine bay the other day there was mouse poop in there. The car did a lot of sitting over the past 5 years.
Thank you. That’s some good info
I did check the levers on the mufflers and both move easily, the hoses are also still hooked up to the actuators. One thing I forgot to mention is when changing the solenoid in the bumper there was suction on the input vaccum line when I pulled it off from the solenoid. So apparently there is vaccum of some degree happening. It’s possible that I either recieved a bad solenoid or the remote I was using is defective. It came with two remotes so I’ll try the other one tomorrow.

I'd just test it with a good fuse and without the M2W system to rule that out.

Yeah good idea I’ll do that tomorrow and follow up

On mine i found the vac line pinched by the rear bumper, only one valve would close. I ended up capping them off and leaving them open full time, my car has the M2W box on it but I don't think it works.

I will check that this evening. Neither one of the actuators even attempted to work so I feel like there’s no vacuum at all but I’m going to pull the hose off that goes into the solenoid this evening and see if I can feel any vacuum on it

If you can connect both hoses together that are attached to the solenoid, then what should happen if the vacuum lines are ok, the butterflies will close when you start the engine. If they do close, then the problem is with the solenoid, the fuse, wiring, or the exhaust module controller (which is in the rear of the car). The controller decides when the parameters have been met to cut power to the solenoid, thus spilling the vacuum and allowing the butterflies to spring open. It’s also the case that if one of the actuators are damaged, that the resulting vacuum loss can be enough to keep the other one open too. There’s a lot that needs to be checked out to solve this issue.

Well now I’m really confused. I replaced the solenoid and the Mild to Wild still wasn’t working… I took out the mild to wild unit and just put a fuse back in and the mufflers are working as they should. So it’s looking like maybe my mild to wild unit is defective, I don’t know of any way to test that though. I guess I’ll send it back and try another one.

Ur killling me man. Im already stressed with ur other situation.

ah this isn’t nearly as concerning but still something that isn’t working right. I swear every car I buy has so many issues. I came across an alternate way to connect the mild 2 wild so gonna give this a try later

The add-a-circuit that’s attached to the wiring harness of the M2W unit has a fuse. Did you test that one? If it’s blown, the exhaust control module will never get power, so neither will the solenoid. It’ll be open all the time. Should have been the first thing you checked. And the add-a-circuit that plugs into the EXHMDL fuse location has to be oriented correctly. If you plug it in rotated180°, then it won’t work either.