cmonkey713

In looking at the system on a 2012 convertible with a factory installed NPP, the butterfly valves are free and seem to be in working condition. Tracing the vacuum lines down they seem to be intact and attached how and where they should be. Both valves stay open and will not close. I looked at the fuse block diagram and can't seem to identify a fuse which operates the system. Does anyone have any ideas where I can look? Thanks

Gary '09 C6

there is a 10-amp fuse in the passenger footwell area fuse-block that controls the NPP exhaust--bottom right side of the box.

Steve Haefner

There is a fuse for sure in the pass footwell, most likely previous owner pulled the fuse.

lynnt

What he said ^^^^

HK770

Only for fuse location


http://www.ecklerscorvette.com/asset...ette/50426.pdf

z28hugger

Agreed with what other posters said. If it is not the fuse, I have the factor service manuals for 2010 and I live in Edmond. Send me a PM and I will be glad to make copies or we could meet somewhere so you could look at the manual. It contains a detailed step by step procedure for diagnosing the NPP. Good luck!

Dano523

Either the NPP 10 amp fuse has been pulled or blown,


The NPP solenoid in the rear bumper cover has melted in the open position (passenger inner tail light removed, straight down under the rubber cover),


Of you have a break in the vaccum line between the intake manifold to the NPP muffler valves.

Items in the back of the car,


Where the vacuum line starts on the back of the intake manifold and then goes to the back of the car.


Or someone installed an aftermarket NPP controller that the unit is cooked or it's fuse is blown.
If you see this at the fuse box, then an after market controller was installed,

owc6

Not seeing a problem with them staying open all the time.

okie08vette

Did you get it figured out?

z28hugger

Dano523 - excellent info and pics.

HANNY

I agree that's first class post by dano,,,,, the vacuum actually "closes" the valve (that's why they open when you shut the car off) at least 3 possible issues ill list first as most common
1. The fuse is blown or missing, if you have the mild to wild it could be the unit itself malfunctioning
2. No or low vacuum at the valves (easy to check just pull each hose off and check for good vacuum, if you have a vacuum pump with a gauge it should be somewhere around 20-25 at idle)
3. the npp valves them selves are bad, usually only one would go bad not both at once but its plausible I suppose.

hope this helps, paul

blittle

Absolutely!

Not So Fast

As always, Dano523 to help
Silly question but have to ask, is the FOB battery good???
NSF

cmonkey713

Thanks Dano! Perfect pics on how the system is laid out and where and what to look for.

blittle

......but good question!

Dano523

No worries, and start but pulling passenger inner rear tail light, and with the car running, disconnect the in line off the silionid to check for vaccum on it from the intake manifold.

The NPP system controls the solenoid, hence until the solenoid sees power, it remains closed. So the quick way to see if you have a breaks in the vacuum line from the intake manifold to the solenoid, or if the problem is just the solenoid to the mufflers isntead.

As for the solenoid you can pop off the connector on it to check for voltage at the connector with the car running to check for problems back up wiring instead. Hence if you get 12 volts on the solenoid connector pins, then the NPP module is working. If you don't get 12 volts, then mulitmeter off the ground of the car, and check the connector pins wire tn/white with the negivite probe to direct chassis ground isntead. Hence the NNP module may be sending the 12V to the connector on the TN/Wt wire, but the ground connector pin wire (black out of the connector) has a problem to chassis ground instead.

So this weeds the problem down to either the solenoid or the lines after the solenoid if the connector has 12 volts on the pins, and you have vacuum out of the solenoid.
So in vacuum line connected back the solenoid, it having 12V to open it with the car idling, disconnect the out line on the solenoid and see if you have vacuum on the out port.


If you have a vacuum out of the solenoid, the you know that you have a problem with the lines and reserve ball in the back isntead.

To be blunt, the hardest repair your going to have is if you have no vacuum from the intake manifold to the "in" port on the solenoid with the car running. Hence get to find where the vacuum line has the problem between the two isntead.

HANNY

agreed, basically if both don't work/close then you have no power to the solenoid (fuse blown or computer isn't energizing it (the fuse which in turn runs to the solenoid) or wiring issue,unlikey tho)
or you have no vaccum back there to the solenoid and then to the exhaust solenoids.

Car running: I would start easy at the fuse under the passenger feet and a simple check it has power on both sides of the fuse (no power on one side then its blown which indicates a harder problem to diagnose but not too bad) , then if its got power while the car is still running go to the solenoids on the exhaust and pull the vacuum line off one of them (since they are connected and check both vacuum from same place) if its there the exhaust pod/solenoids are bad at the exhaust. If no vacuum pull the rear fender/trunk facia off and check vacuum there, if no vacuum trace the leak back to the intake. if you have vacuum then check for power at the solenoid and a good ground as well.

my guess if you have power at the fuse is? The solenoid behind the trunk facia. but you need do check the other stuff first. good luck. You should have plenty enuf to find and fix the cause with Dano's diagrams and this post here. good luck, paul