NPP Confusing me
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Joined: Mar 2017
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From: West Palm beach Florida
NPP Confusing me
All, trying to figure out my 2012 GS with factory NPP. Everything has been perfect on the car for a year then all of a sudden the NPP starts acting up. It is factory except of the LG cutout switch in the shifter handle. Here is the situation. Valves open prior to start. Valves close after 1-2 seconds after start. Valves stay closed at idle and under load, never opening at the 3500 RPM and above (they use to, and its easy to hear the difference before). I can activate the cutout on the shifter and the valves open as long as I want them to be. When I use the shifter button again the valves close and its quiet again. Am I in assuming correctly that if the shifter switch opens the valves, then the solenoid is operating correctly? Im confused and don't want to just replace parts.
thanks for your advice.
thanks for your advice.
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Joined: Jun 2005
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St. Jude Donor '15
"In honor of jpee"
I'm no techie and with that, my thoughts are you do have a problem if everything was working as it should up until recently. I would think it's something in the programming/computer that controls the NPP. Some aspect of the NPP program is not being told that the car's exhaust flaps should open and close at a certain rpm/throttle position (with, or without the LG NPP shifter **** activator). My guess is that the solenoid is acting correctly. Time for diagnosis of the problem. Hope others will join the thread!
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Bring me up to speed on what the LG cutout switch is controlling.
Do you have muffler cuts outs, or is there something like a mild to wild type module that the LG cutout switch is controlling, to control the NPP module power instead.
Lets make it easy, and just remove this fuse, or if there is a add a fuse type connector in that fuse location with a fuse, then remove the entire add a fuse as well.
This should start the car up in loud mode, and it should stay in load mode. If the car starts up in quite mode, and stays in quiet mode, then the NPP pneumatic solenoid valve is having problems.
Now put just the 10amp fuse back in that location, and remember that the the mufflers will not open until you get to 3500 RPM, and have the gas pedal pushed down at least 60% down.
If your are good on the two above test,
then really need to know that the LG cutout switch is controlling, to trouble shoot farther.
Is the controller just controlling the fuse on the fuse box, or is there another module that was added into control the power to the fuse box instead.
Do you have muffler cuts outs, or is there something like a mild to wild type module that the LG cutout switch is controlling, to control the NPP module power instead.
Lets make it easy, and just remove this fuse, or if there is a add a fuse type connector in that fuse location with a fuse, then remove the entire add a fuse as well.
This should start the car up in loud mode, and it should stay in load mode. If the car starts up in quite mode, and stays in quiet mode, then the NPP pneumatic solenoid valve is having problems.
Now put just the 10amp fuse back in that location, and remember that the the mufflers will not open until you get to 3500 RPM, and have the gas pedal pushed down at least 60% down.
If your are good on the two above test,
then really need to know that the LG cutout switch is controlling, to trouble shoot farther.
Is the controller just controlling the fuse on the fuse box, or is there another module that was added into control the power to the fuse box instead.
Last edited by Dano523; Jan 28, 2018 at 11:17 PM.
Thread Starter
Advanced
Joined: Mar 2017
Posts: 81
Likes: 3
From: West Palm beach Florida
Bring me up to speed on what the LG cutout switch is controlling.
Do you have muffler cuts outs, or is there something like a mild to wild type module that the LG cutout switch is controlling, to control the NPP module power instead.
Lets make it easy, and just remove this fuse, or if there is a add a fuse type connector in that fuse location with a fuse, then remove the entire add a fuse as well.
This should start the car up in loud mode, and it should stay in load mode. If the car starts up in quite mode, and stays in quiet mode, then the NPP pneumatic solenoid valve is having problems.
Now put just the 10amp fuse back in that location, and remember that the the mufflers will not open until you get to 3500 RPM, and have the gas pedal pushed down at least 60% down.
If your are good on the two above test,
then really need to know that the LG cutout switch is controlling, to trouble shoot farther.
Is the controller just controlling the fuse on the fuse box, or is there another module that was added into control the power to the fuse box instead.
Do you have muffler cuts outs, or is there something like a mild to wild type module that the LG cutout switch is controlling, to control the NPP module power instead.
Lets make it easy, and just remove this fuse, or if there is a add a fuse type connector in that fuse location with a fuse, then remove the entire add a fuse as well.
This should start the car up in loud mode, and it should stay in load mode. If the car starts up in quite mode, and stays in quiet mode, then the NPP pneumatic solenoid valve is having problems.
Now put just the 10amp fuse back in that location, and remember that the the mufflers will not open until you get to 3500 RPM, and have the gas pedal pushed down at least 60% down.
If your are good on the two above test,
then really need to know that the LG cutout switch is controlling, to trouble shoot farther.
Is the controller just controlling the fuse on the fuse box, or is there another module that was added into control the power to the fuse box instead.
The LG switch is basically a mild to wild in the shifter ****. all it does is replicate the same as pulling the fuse. When you press the button it basically breaks the circuit as if you had no fuse at all. Then you can press it again and have the OEM system functions. I find it nice to not have to fumble for a remote, I can open and close the valves right from the shifter.
Race Director
Joined: Dec 2013
Posts: 12,502
Likes: 3,628
The LG switch is basically a mild to wild in the shifter ****. all it does is replicate the same as pulling the fuse. When you press the button it basically breaks the circuit as if you had no fuse at all. Then you can press it again and have the OEM system functions. I find it nice to not have to fumble for a remote, I can open and close the valves right from the shifter.
If it is, then the glitch may be when you cut the power to the NPP module with the car running, a glitch in the NPP module programming or GM land bus, and the module is not seeing the BCM throttle position/RPM point to drop the power to the HPP vacuum solenoid isntead.
If it not, then you have a problem on the GM land bus and the Npp module is not seeing the BCM throttle position/RPM point to drop the power to vacuum solenoid instead. Hence default state once the NPP module gets power, is to power up the vacuum solenoid.
If you want to monitor the NPP controller, easy to do with a tech II as your driving the car with someone checking the tool to see if its getting the needed data to change state to drop the power to the vacuum solenoid at 3500/60+ throttle in the first place.
Last edited by Dano523; Jan 29, 2018 at 03:41 PM.
