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The fuse is in the box under the hood on the passenger side. There are pics in the thread about location or in the manual.
I'll save you 30 seconds of looking for the fuse box picture from Theta's post in this thread. It shows the yellow 20A fuse to pull. The location for 2014 & 2015 is the SAME. Only the number of the slot is different:
The Engine Sound Management in the latest settings implementation on the 2015 A8 and Z06 (see below) are progressively more aggressive (valves open earlier and longer) than the original ESM settings available (originally only Auto or Off, and some M7 still have the original menu). Currently the reports from the Z06 M7 owners are that Track mode in ESM settings are 100% open all the time.
*** This is the new ESM screen in Z06 and the few A8 2015 I've seen. Someone with a recent 2015 M7 please let me know if this is what you see so I can update the master NPP thread. I need a 2015 M7 owner with the new menu to confirm Track ESM setting is the same as the Z06 behavior. This would mean NPP fuse pull is the same as Track ESM mode. Pay special attention to the 1700RPM hitch described in the master thread. It is confirmed that the Z06 does NOT do this in Track mode. If confirmed this would mean no reason to pull the NPP fuse if you have the new NPP menu settings.
Additional notes (to save parsing the threads):
The V4 (AFM) valves on an M7 car will only ever close in Eco mode as this is the ONLY time the M7 can be in V4. The A8 can enter V4 mode in ALL modes except manual shift (paddles) and there will be a quieting effect in V4 with AFM closed. V4 with AFM valves open (and CEL) sounds awful.
The valves are fully electronic. There are separate fuses for the AFM and NPP valves. NEVER pull the AFM fuse (causes CEL). You CAN pull the NPP fuse (#42 for 2015 cars) without consequence. This is the same as the Track setting in ESM by all reports. So really no reason to pull the NPP fuse if you have the new NPP menu settings.
My understanding from the C7 general side is that in the off mode the valves are open at start up then close under 1750 rpm. If you pull the fuse it's open all the time. I don't have my car yet so can't confirm.
My understanding from the C7 general side is that in the off mode the valves are open at start up then close under 1750 rpm. If you pull the fuse it's open all the time. I don't have my car yet so can't confirm.
That's not quite right... The discussion in this thread by all involved has been far more focused and thorough than the fragmented, frequently inaccurate comments about the NPP functionality in General or Z06.
The behavior of M7 vs. A8 are different. Assuming you are talking M7, Engine Sound Management Off will leave NPP valves open all the time...EXCEPT from 3rd gear on up when revs fall below 1700RPM. This is the 1700PRM hitch. Most noticeable on upshifts when revs drop below 1700 and then you tip in. With ESM Off the valves will ALWAYS be open at idle. Pulling the NPP fuse fixes ONLY this 1700RPM issue for the M7. The Z06 does NOT have the issue, and I'm waiting to hear about the newest 2015 M7 NPP cars with the new ESM menus. Not worth it on the A6/A8 due to constant V4 mode.
However, as described above you post, there are new ESM options in the Z06 and the A8 C7 NPP. I am waiting for someone with a newer 2015 M7 NPP to confirm what the ESM menu says. The manual still shows only Auto and Off - as in it does not show the new options in the PDF online manual.
I am waiting for someone with a newer 2015 M7 NPP to confirm what the ESM menu says. The manual still shows only Auto and Off - as in it does not show the new options in the PDF online manual.
I have an early production 2015 (1st week, VIN 608) M7, NPP car and it has the multiple selections for engine sound management: Stealth, Touring, Sport, Track. It also exhibits the cruising below 1700 RPM valve closure. Exhaust volume gets noticeably louder as RPM's increase above 1700 RPM -- even in the "Track" setting, which is where I typically leave it.
I have an early production 2015 (1st week, VIN 608) M7, NPP car and it has the multiple selections for engine sound management: Stealth, Touring, Sport, Track. It also exhibits the cruising below 1700 RPM valve closure. Exhaust volume gets noticeably louder as RPM's increase above 1700 RPM -- even in the "Track" setting, which is where I typically leave it.
Ernie
Has anyone checked to see if earlier computers could be reflashed to gain this functionality? I wasn't sure if it was an update or a new computer or software providing this capability. I have a 2014 M7 and would love to have this and not have to worry about coming up with my own solution to solve for the 1700 tip in.
Has anyone checked to see if earlier computers could be reflashed to gain this functionality? I wasn't sure if it was an update or a new computer or software providing this capability. I have a 2014 M7 and would love to have this and not have to worry about coming up with my own solution to solve for the 1700 tip in.
No, that is in the BCM, and nobody has reported being able to gain access to it yet. Theta mentions this in the thread here I believe.
I have an early production 2015 (1st week, VIN 608) M7, NPP car and it has the multiple selections for engine sound management: Stealth, Touring, Sport, Track. It also exhibits the cruising below 1700 RPM valve closure. Exhaust volume gets noticeably louder as RPM's increase above 1700 RPM -- even in the "Track" setting, which is where I typically leave it.
Ernie
Ernie, thank you for definitively confirming! I will update the main thread shortly with all the latest. So we get more menus, but only the Z06 gets what we want in Track. Why there is the difference is anyone's guess. Oh well.
**** Another request, if someone could post a picture of the 2014 Engine Sound Management screen with Auto an off, that would be great. Mine is away for the winter and can't take the pic myself. I want to consolidate everything in my OP.
Updated the OP to reflect the latest knowledge. 2015 M7 Stingrays have the new ESM menu options. Original Off = Track. 2015 M7 Stingray even with updated menu, Track has 1700RPM hitch. Z06 Track does not have hitch. So M7 Stingray owners can try the fuse 41/42 pull and see if they like it more. All others (A6/8 and Z06) probably won't get anything out of a NPP fuse pull.
So, I finally took the 30 seconds and pulled the fuse in my 2015 M7. I did this because my NPP exhaust was making a squeak noise whenever it opened or closed. Took it to the dealer and they said Chevy doesn't have a fix for it. After pulling the fuse, the car sounds and acts like it should have on Track mode to begin with. It's loud all the time, not just when it's over 1700 RPM's. I wish I had done this since day one. Only thing I don't understand now, is why does it take pulling the fuse for it to sound like it should have from 600RPM-6500RPM? Dunno what the auto sounds like, but if you have a M7 I'd highly suggest you spend 30 seconds and try this and see if it's not 100% better.
So, I finally took the 30 seconds and pulled the fuse in my 2015 M7. I did this because my NPP exhaust was making a squeak noise whenever it opened or closed. Took it to the dealer and they said Chevy doesn't have a fix for it. After pulling the fuse, the car sounds and acts like it should have on Track mode to begin with. It's loud all the time, not just when it's over 1700 RPM's. I wish I had done this since day one. Only thing I don't understand now, is why does it take pulling the fuse for it to sound like it should have from 600RPM-6500RPM? Dunno what the auto sounds like, but if you have a M7 I'd highly suggest you spend 30 seconds and try this and see if it's not 100% better.
I like the fuse out as well (obviously). But the squeak is either the valve or actuator. And I'd guess the valve. If you are so inclined, you can move the NPP valves by hand to figure out which one it is. Just stick your fingers in the exhaust tip and move the butterfly. They are spring loaded open, so rotate them closed. The fix is either a new actuator or axle back, and warranty will cover it. Definitely not normal.
I would like to thank you from the UK. I have one of a very few C7 on this side of the pond and was delighted with this info as I also feel the car is to quiet. M7
Happy to help, and I'm glad others find it helpful!
Ironically, just yesterday I got a 2015 Z51 with the A8 transmission (had a 2014 Z51 M7 previously). In my 50 miles of driving it conservatively for break in, there's much more inconsistency with the low RPM NPP behavior in the upper gears compared to the manual. I had ESM set to Track the entire time, and I spent equal time in Drive and Manual with paddle shifting. There seemed to be a "hitch" at around 1900RPM sometimes where it was quiet (despite being in V8 Track mode) and the NPP would abruptly open and be loud. Much like the 1700RPM hitch in the manuals. It also seemed to only happen in 6th gear and up. But it was inconsistent, which was the strange thing. Sometimes it would allow the tip-in lugging boom at 1500RPM, other times it was quiet.
Clearly I know why it's quiet in V4 AFM mode while in Drive, but the manual mode is always V8 and there was obviously valve actuation happening somewhere.
I need to repeat some tests with the NPP fuse (42) pulled to see if NPP valves are the culprit and what the patterns are. But that will be a while since winter shat upon Michigan again today with snow and freezing rain...
Since this thread has managed to stay relevant/cited for so long, I want to keep a reasonably concise list of the collective knowledge from this thread and others. I will update it so that it's easier for people to get the details without parsing the whole thread.
Here's a summary of what I think we collectively figured out in the numerous threads. All details are important:
All C7 have valves for V4 mode in front of the mufflers. We call them AFM valves. Fuse 32 controls the AFM valves, and pulling fuse 32 or AFM connectors will result in a CEL and awful sound in V4 mode.
NPP cars have electronic valves in the outer exhaust tips. We call them NPP valves. Fuse 41 (2014) or fuse 42 (2015) controls NPP valves. Pulling the fuse will NOT cause a CEL, nor will pulling the connectors at the valves. These two NPP valve disable methods are electrically identical, but the fuse pull is simpler and more easily reversible.
Manual transmission cars go into V4 mode ONLY in ECO mode.
Automatic cars go into V4 AFM mode in ALL MODES, except when paddle shifting/sport shift.
The Z06 and newer 2015 Stingray have new Engine Sound Management settings! ESM Off (2014) = Track (2015+) in the below. The Engine Sound Management in the latest settings implementation on the newer 2015 Stingray and Z06 (see below) are progressively more aggressive (valves open earlier and longer) than the original ESM settings available (originally only Auto or Off, and some early 2015 M7 still have the original menu).
Engine Sound Management (ESM) OFF/Track will NOT keep NPP valves open all the time for the 2014-2015 Stingray. Even with the ESM menu update to the 2015 ESM settings, even in the OFF/Track setting, the NPP valves will still actuate by design in certain situations (low RPM, lugging, high gear highway, etc.). Very pronounced in M7 below 1700RPM in 3rd gear and above. M7 owners call this the "1700RPM hitch".
Driving Mode (dial) does affect NPP behavior with Engine Sound Management (ESM) on Auto. However, that's subject to most of the below when OFF or in Track in the newer ESM mode settings above.
Driving Mode does not alter sound when NPP valves and AFM valves OPEN during V8 operation. This is the loudest the NPP exhaust can be both at idle and while driving, and Driving Mode doesn't change the sound when both sets of valves are open.
The awesome raspiness at cold start is not an NPP function. It's a fueling and ignition condition that only exists at cold start (unfortunately) that quiets down to 'normal'. Fuse pull or ESM setting will not change this.
V4 operation will close the AFM valves and make the exhaust quiet even with NPP valves forced open (fuse 41/42 pulled). This is the biggest reason A6/8 owners may feel the NPP exhaust is 'too quiet' off throttle since it can spend so much time in V4 mode.
In M7 Stingray cars, pulling NPP fuse fixes ONLY the 1700RPM hitch that some (like me) find annoying and prevents NPP valves from closing at highway cruise even with ESM OFF/Track.
NPP valves open all the time and V8 operation will result in hearing/feeling more low frequency content at low RPM all the time (highway especially). Some may like this, some may find this 'drone' objectionable.
Once NPP fuse is pulled, ESM obviously no longer has any effect, so you give up push button 'stealth mode'.
In automatics, pulling NPP fuse has negligible effect due to nearly constant V4 operation in low RPM/low load conditions. It gets quiet when AFM valves close...and therefore it's quiet even with NPP fuse pulled or ESM OFF/Track. The 1700RPM hitch has not been reported in automatics.
Disabling V4 in automatics outside paddle/sport shift requires a tune or Range Technology OBDII plug (http://www.rangetechnology.com/).
There is not yet a documented solution like a Mild2Wild switch for the electronic NPP valves. They are PWM controlled. There was rumor a vendor was working on something, but there was quite a lot of experimenting on simple solutions with no luck.
All the intricacies of the above essentially mean that the M7 and A6/8 folks will have a different experience with the NPP. I feel the M7 Stingray owners will really notice the difference when pulling fuse 41/42, but you give up some control. It's worth a try though, IMO. Automatic owners will hear little or no difference between ESM OFF/Track and fuse 41/42 pulled. This is due to the automatic's nearly constant V4 operation off throttle/low RPM/low load in all driving modes. So I personally don't think pulling fuse 41/42 makes much sense for auto owners.
The location for 2014 & 2015 is the SAME. Only the number of the slot is different:
UPDATE 4: For this past week, I have set Engine Sound Management back to Auto with fuse 41 removed in order to validate no CEL in this mode as well. Driving in Tour and Sport, no CEL. I was concerned that constant calls for the NPP to be closed in these modes (rather than just the 1700RPM hitch in ESM Off) may cause an issue. This is also important since any external switch would want to rely on ESM Auto as the base state which the switch would then override for 100% open NPP.
UPDATE 3: Fuse 41 only pulled for a week. 3 trips to and from work and about 8-9 start-stop cycles. NO CEL!!! All this really solves is the 1700RPM NPP issue. What you give up is on-the-fly changes to Engine Sound Management, so 100% open NPP all the time. V4 mode is unaffected.
I have only been operating in Engine Sound Management OFF. Not sure why it would make a difference in CEL if set to AUTO, but I wanted to mention it.
I like it better, but I can understand why the NVH guys may have done this. The bass resonance is noticeable in the upper gear tip-in lugging as described previously. However, I like it better as I can hear what the car is doing all the time.
So it -appears- that the LED fuse may not be necessary to prevent CEL. Theta's control box would be the long term solution.
UPDATE 2: CEL cleared when fuses replaced and restarted about 5 times.
Fuse 41 controls the NPP rear valves. With 41 gone and 32 in place, Engine Sound Management has no effect. I will assume for now that 32 is the front V4 valves.
Will try driving without 41 only and see if it throws a CEL. I suspect it will since I recall another member got one when his NPP valves froze in really cold weather.
UPDATE 1: Got a CEL on the way home. Replaced fuses and restarted a couple times. CEL Still on. Will give another couple tries tomorrow to see if it clears before calling OnStar. Hopefully it's not a coincidence with a real CEL.
V4 mode is very coarse sounding. A bit like a tractor. Sound seemed to noticeably increase interior vibration and seat resonance at highway speed. Added unpleasant booming.
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Original post:
Cliff's Notes version: pulling fuses 32 and 41 in the front fuse box (engine) leaves BOTH the front and rear exhaust valves open for all driver modes and V8/V4 modes. No CEL.
I had read here and another forum about this trick, so I tried it today to see what happened. The C7 manual (page 10-39+) shows fuses 32 and 41 control exhaust valves 1 and 2...so I pulled them.
I have an M7.
Observations:
Engine Sound Management selections have no effect, as expected.
V4 mode sounds crappy. Forced it to V4 in Eco mode...and switched out 5 seconds later.
The behavior on low RPM throttle tip-in (on upshifts especially) where the sound is quiet and then valves open at about 1700 RPM is gone. Again, as expected.
There was no CEL thrown in my drive to work (~35 minutes).
There -may- have been more drone on the highway in 6-7th in V8 mode, but I need to pay more attention and update this comment. The reason I am doubting myself on this is it would imply some sort of closing of one or both sets of valves in normal "open all the time" operation.
So the experiment was a success, but I am not sure if I will leave it this way. For me personally, the only minor annoyance of the standard NPP "open all the time" setting was #3 above; it was too abrupt and on/off for my tastes. Not that big a deal, since with the fuse pull V4 mode is not nice and there no -option- of going quiet while driving.
I think the A6 folks would not like the results since, from my understanding, V4 can happen in most/all modes (maybe except Track?). For M7 folks, stay out of Eco. Of course if you tune out V4, then it's not a problem.
I just wanted to personally thank you guys so very very much for this thread, it truly is exciting to say the least
Nothing makes a man feel like a man, (besides a good looking women with him) then a true Muscle car / Super car Engine with deep rumble.
Like ALI use to say " Rumble young man Rumble " - boy you feel like the man.
The look of Ferrari, the sound of a " Watch the Hell Out - I'm coming thru "
Man this is what I was looking for, because like you all I do Not want to void the expensive warranty I have purchased, & thanks to you all ............... I can satisfy my pallet & quench my thirst of Loud Vette Sound
Please Note this great trick keeps me from straight Piping it.
However Let me ask you will that Range Technology OBDII plug that you spoke about ? Will it leave a Mark ?
or Void C7 Warranty ?
Also thanks so much again guys I truly do appreciate it as I really did want long tubes but without a tune - but when I heard a check engine light will come on without a tune ........ That eliminated that
Hey as a side point even though I don't have a super easy trick like you all, let me try to add value to this conversation by giving some feedback on my Warranty Friendly Mods to my 2015 C7 Z51 8-Speed Auto
Free Up horsepower WITHOUT VOID OF WARRANTY: (Keep in mine Stock rear wheel horsepower = 411 rwhp)
10hp - 20hp - K & N Air Filter Replacement Only (Finally Had Installed on mine)
Grand Total Modded Horsepower to my vehicle should = 440rwhp
(However with this much hp & even though sizable increase may Not necessarily feel the difference unless you turn off T.C.S. & Stability Control) = Tapping the center **** button twice - 2x
Hope that helps let me know what you think, lastly I had the Z06 Clear taillights installed in place of the red stingrays ones - let me know & thanks so much again for this trick hopefully this pays it forward
However Let me ask you will that Range Technology OBDII plug that you spoke about ? Will it leave a Mark ?
or Void C7 Warranty ?
From what I've read here based on C7 owner reports, the Range Technology does not leave any marks. It does nothing other than prevent V4 operation. The only potential downside is that it draws a small amount of power when the car is off, so it should not remain connected for more than a few days of storage. This is also stated on the web site.
Hey guys thanks to you all I thought I would put up a video of the results thanks to XP80 Assoc.
Here it is,and boy what a difference, I love it especially when you turn a corner, Wow
Not to mention turn off the TVS + Stability for Max results
Also just put LED Daylight Blue Bulbs in the Cargo BAY Area as well as the License Plate holder, instead of the traditional factory artificial lighting
I am only dreaming about a C7, that's why I'm reading about the NPP exhaust. The simple way to make this driver controllable would be to put a switch on the wire at pin 34 of the chassis module. The wire will be light green with a violet stripe. Result will be switch closed = stock, switch open = NPP valves default to stuck in open position.
The switch wouldn't even need a relay because it is the low current control side. And it won't trip the CEL because there is no feedback circuit unlike the upstream cylinder deactivation valves that do.
I am only dreaming about a C7, that's why I'm reading about the NPP exhaust. The simple way to make this driver controllable would be to put a switch on the wire at pin 34 of the chassis module. The wire will be light green with a violet stripe. Result will be switch closed = stock, switch open = NPP valves default to stuck in open position.
The switch wouldn't even need a relay because it is the low current control side. And it won't trip the CEL because there is no feedback circuit unlike the upstream cylinder deactivation valves that do.
DO NOT FOLLOW THIS ADVICE
I'm sorry - and I'm really not trying to be rude here - but this is why I left this thread. So much information gets twisted, and everybody wants to either debate what works, or come up with something that is unnecessary. Don't let this deter you from getting a C7 - we have a lot of good technical information posted, and I think you'd get a kick out of most of it.
I'm not going to debate this one - I'm simply going to post that bolded advisory and hope people take heed. The CCM should not be touched - that's the equivalent of physically removing the valves. We have no idea what this causes in the form of a log, internal error code, etc. regardless of a CEL posting. Use an MDI on these cars and you'll see a ludicrous amount of bus errors. Basically, it would show up as 'valve not responding' in the CCM logs. Most importantly, tapping that wire (even with a PosiTap) voids the warranty on the CCM (keep reading), and subsequently the BCM if found. If/when you have any issues with your modules, you're SOL. BCM/CCM/ECM/TCM wire and flash modifications are now handled a different way beginning March 10, and you will be blacklisted in the system. I've debated posting that service bulletin... It goes into detail about tapping even a single wire to or from any of the control modules. You don't have to believe me - it's not like I have a warranty to worry about anyway.
Secondarily, assuming that this didn't cause issues and was warranty-friendly, it sure is a pain in the butt to remove the rear carpet, rear electronics partition protector, pop the terminal, wire forward, etc. I agree that it would be neat if it was a sound idea - I toyed with the idea of placing an in-cabin wireless relay on that wire (as the external ones were unsuccessful) until we knew more about the CCM, itself.
The switch, that I have correctly running (and now have another 10 of in the field) is extremely simple. You do not splice or interface with the CCM - I posted that diagram at the first of last year, and it took months until we realized that the polling rate is controlled by PWM. This was an especially big pain-in-the-butt for people trying to do conversions to NPP without the CCM assisting.
The correct (and extremely simple) way to do the switch is simple: have two leads running from fuse 41 (or 42 for 2015), sever the middle of the fuse, and run the wires back into the cabin. There are several panels to place a small SPST switch, but I do have a favorite since it's easy, and is very nicely accessible. Once you have your wires running into the cabin, and the switch wired, use a 15A in-line AGC relay (or in-line ATM/ATC) to protect the circuit, and wire both leads to the SPST.
You now have a proper mechanical switch that is only turning power on and off.
I will be happy to post pictures of this (or most likely link as a new How-To), as it is 100% reversible, and the panel used can be replaced for $40. Takes all of an hour, and the parts list can all be purchased at AutoZone or Lowes.
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I will be happy to post pictures of this (or most likely link as a new How-To), as it is 100% reversible, and the panel used can be replaced for $40. Takes all of an hour, and the parts list can all be purchased at AutoZone or Lowes.
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I like the fuse out as well (obviously). But the squeak is either the valve or actuator. And I'd guess the valve. If you are so inclined, you can move the NPP valves by hand to figure out which one it is. Just stick your fingers in the exhaust tip and move the butterfly. They are spring loaded open, so rotate them closed. The fix is either a new actuator or axle back, and warranty will cover it. Definitely not normal.
