BigBilll

The dual mode exhaust feature stopped working on my 2013 427 Convertible. I really thought it was the vacuum solonoid that's behind the passenger tail lamps, replaced and still not working. Flaps are stuck wide open. I have good vacuum up to the solenoid. Fuse is good, and same problem with mild to wild removed, no blown fuses anywhere. Fully charged battery, all grounds have been cleaned/ tightened. I believe its a bad control unit. My question is the LS3 cars have control unit #1587909. and they claim this is for all NPP exhausts. My control unit is part #20822685 and has a sticker on it that says LS9, and I do realize although very different, LS7 and LS9 are lumped together for some things, including this section of the forum. I did order the same part # that came with my car, just puzzled by the different part numbers. Different calibration is my guess?? And the correct one for the LS7 / LS9 is $30 more than the LS3 version. They look identical on the outside, except for the part number sticker. Thoughts?

dmuellenberg

I don't have an answer to your question, but just a suggestion. I know it's a long shot, but did you see if the flaps can freely move/close? Easy to check, maybe the flaps are stuck open and that is the issue.

Hib Halverson

Was DTC P166A set?

449er

Better stuck open than closed

corv1998

Yes,exactly see if the flaps move easily. A few moving parts on there plus a diaphragm.

BigBilll

I don't know if that code has been set, I will have to scan to see. Hib, I know you really know the C6 as well as much useful information ! Much respect, and I will report back to you. Mucho Gracias!

BigBilll

Flaps move very easily. Had an extra accuator. swapped out, lubed pivot shafts. Nothing

BigBilll

No... but 0054, 0056 and 0060 were... I'm going to look those up. I know I've got good vacuum to the solonoid, because I heard a long hiss of air/ vacum when I went to swap it out.

ZR1Cat

OP, after reviewing your posts, i can't offer any helpful suggestions. But, please keep us updated on your progress.

BigBilll

I worked on the car last night, and I believe I have a badly leaking vacuum actuator. One actuator moved the flap and held vacuum no problem, the other one I can move manually / easily. It will not hold vacuum and will not move with my vacuum pump attached. I have a known good actuator and will swap that in and see what happens.
I believe that if there's a decent vacuum leak anywhere after the solenoid, the system will not work at all, and flaps will remain in the open mode. It's no fun working on the NPP feature of the mufflers, I put the car on my lift and drop the mufflers off their respective hangars, still tight with my fat hands and sitting on my fat ***. lol
I love the car loud! But the factory quiet setting while cruising on the hwy. is great when you're not zooming around and want to crank the music and enjoy the peace of the cruise. I'm also a long time Harley rider, and I know that continued loud noise can be very fatiguing. My Harley is no longer loud as well, just a nice tone. I will post results. I have wayy too many hours invested in this exhaust to give up now!