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HOW TO: Disable AFM Exhaust Valve Actuators with HP Tuners
Many people have found that the AFM exhaust valves for Non-Z06 cars can have issues and fail when the car is driven hard in a track setting. Additionally, these valves cannot be “deleted” without the computer freaking out and throwing codes. Until now! We’ve figured out how to remove these valves, and adjust the tune using HP Tuners so that the computer does not think there is anything wrong!
To do this you will need:
HP Tuners with VCM Suite UPDATED TO VERSION 3.6 and two additional credits NOTE: The credits needed for this are IN ADDITION to the credits used to tune the ECM. This means that your C7 will use a grand total of 4 HPT credits, two for your engine tune, and 2 for the FSCM tune!
Taken from the HPT forum: As of Software version 3.6 you can now tune the FSCM/C304 modules however they do cost additional credits in order to license these modules which you will notice once you attempt to flash them. If you have no plans to tune/modify either of these modules then when you start the read process simply select DO NOT READ on the modules you have no plans to modify, this way the software will not ask you to license them. Keep in mind these modules cannot be read via the bus so a stock file is generated for you(you will see a popup that will state this clearly as well).
•1 credit each for FSCM A-F
•2 credits each for C304(C7 Corvette)
To clarify, I am referring to the valves circled in RED in the below picture. We are NOT talking about the valves circled in Green! The valves circled in RED are the AFM valves and are related to Displacement on Demand / Active Fuel Management for “Eco mode”. They serve no other purpose, which is why the Z06 does not have these valves since it does not have Eco mode.
In order to remove these valves from the exhaust, you will need to be able to stop the computer from thinking there is a problem by turning off the codes it throws. The main reason that we could not do this previously is the codes that are generated to illuminate the check engine light (CEL) when these valves are disconnected is not located in the ECM, but rather the FSCM. The same result happens when pulling fuse #32 under the hood as this also disables the AFM but the computer trips out as it thinks there is a problem. The FSCM module handles these codes which is also known as the C304 module.
For testing this, I pulled fuse #32 from the under hood fuse box and after two engine startup cycles received these 6 codes:
The first code is a master code, and the other 5 are individual codes. P26C8 will not throw unless something else throws first. So what are these codes for? Let’s look in the manual. First the P26C8 code indicates this: “Chassis Control Module Requested MIL Illumination”. Again, like I said this is a master code. When the other 5 codes came up, it triggered P26C8 which is the actual code that turns on the check engine light. What do the other codes mean? Lets look:
As you can see, they ALL relate to “Cylinder Deactivation Exhaust Flow Valves” which are the AFM valves in question.
Cool. So all I need to do is turn off the code for P26C8 then right? Whoa there killer… way wrong answer!!
If you turn off P26C8 from working, then you will not get notified for ANY other alert that the C304 module controls! The correct way to do this is to disable all the “Cylinder Deactivation Exhaust Flow Valve” codes individually and leave the P26C8 code fully enabled! If you do the job right, none of the AFM valve codes will trigger P26C8 and you are good to go!
Ok so how do I fix this already?!?!
As mentioned earlier, you’ll need HP Tuners and the VCM Suite installed on your laptop. It MUST be updated to version 3.6 or later or you will not be able to get to the FSCM module to proceed.
Open the HP Tuners VCM Editor software.
Make sure you have the HPT module plugged into the OBDII port, turn the ignition on (do not start car though). Go to “Flash” and choose “Read Vehicle”.
You will see a window pop up. First choose “Gather Info”. After it has gathered info you will see a window that looks similar to the below one. Here you can see the E92 ECM which is the main computer and the C304 CCM which is the FSCM module we need to tune. Ensure that the drop down box is set to “Read Entire” for the C304 module and then click the “Read” button.
(NOTE: you do not need to read the ECM module unless you need to change settings related to the ECM tune)
Once the read is complete, it will bring you into the files it read. Here we need to go to the “System” button (number 1 in photo below), and then click the “DTC’s” tab (number 2 in photo below). Now you’ll need to locate the appropriate codes that we need to disable in the list. The codes numbers are those indicated by number 3 in photo below.
Next you will need to locate the codes we need to turn off. I’ll list them here for easy reference:
In the below screenshot, you will see how to turn them off. Uncheck the box next to “SES Enabled” for each of these codes and then if you click on the “Error Mode” to the right of the check box for each code you will see it is a drop down box. Here, choose “No Error Reported” for each of these codes.
When you are done with that, its time to write the tune file back to the car. Go to the “Flash” menu pulldown and then go to “Write Vehicle”. You will get presented with a box as shown below:
This box is indicating to you that two additional credits are necessary to tune this new module with HPT as I indicated at the beginning of the thread. Once you click “OK” you will be given another popup asking if you are sure you want to continue which you will need to also hit “OK” again on.
After this the tune file is written to the C304 module and you’re all done! You are now welcome to disconnect fuse #32, or disconnect the AFM valve wiring harness connector, or even change out the exhaust to a different one that does not have the AFM valves in it at all!
I'm glad that somebody finally figured this out. That said, I'll be the first to say... Two more credits just to tune individual modules?!?! That's a load of BS. I've been using HPTuners since the original serial module (and re-bought when the USB one came out) but this is getting insane. I've never been a fan of the "credit" system.
Ant, If you got rid of the factory AFM/NPP valves and mufflers, do you see room for electric cut outs with aftermarket mufflers?
Im not sure how much room cutouts would need, but from memory I would say no. You woud have to get creative. At this point I have Corsa mufflers on there (will be selling them) and will be going back to a Z06 NPP axle back since it does not have valves.
I'm almost VERY positive that my tuner used these exact instructions after installing this 3" beauty. There was 2 licenses involved - HP Tuners/Corvette + BCM (body control module) that I remember eliminating the multiple valve codes. Thanks!
I'm almost VERY positive that my tuner used these exact instructions after installing this 3" beauty. There was 2 licenses involved - HP Tuners/Corvette + BCM (body control module) that I remember eliminating the multiple valve codes. Thanks!
I need to have this done. My first actuator went (on a borla exhaust) and the dealer refuses to do something under warranty, only option is to replace the mufflers with OEM again he says. So I’m in the Philly area and I’m looking for someone who can do this procedure for me.
I need to have this done. My first actuator went (on a borla exhaust) and the dealer refuses to do something under warranty, only option is to replace the mufflers with OEM again he says. So I’m in the Philly area and I’m looking for someone who can do this procedure for me.
Thanks, Jan
Any shop that tunes GM vehicles through HP Tuners can do this for you.
I'm glad that somebody finally figured this out. That said, I'll be the first to say... Two more credits just to tune individual modules?!?! That's a load of BS. I've been using HPTuners since the original serial module (and re-bought when the USB one came out) but this is getting insane. I've never been a fan of the "credit" system.
Someone needs to develop one that does not require "credits". That is just their way of raping you over and over again and has nothing to do with GM. You would figure after buying it and also making you pay again, they would have better documentation and descriptions that go along with their software. In fact there is almost none and what they do have completely sucks. The software is very good and powerful, but for crying out loud add some info. This IS also marketed towards the amateur/prosumer so at least have some relative documentation.
Is that really too much to as after all this time?
Someone needs to develop one that does not require "credits". That is just their way of raping you over and over again and has nothing to do with GM. You would figure after buying it and also making you pay again, they would have better documentation and descriptions that go along with their software. In fact there is almost none and what they do have completely sucks. The software is very good and powerful, but for crying out loud add some info. This IS also marketed towards the amateur/prosumer so at least have some relative documentation.
Is that really too much to as after all this time?
Don't get me wrong it's a great tool, better than EFILive IMHO. However it seriously lacks in the help department along with documentation. I'm not asking them to tune it for me, but it would be nice for say the private (beginner/novice) sector to have some kind of roadmap, better description of the tables and perhaps some guides on setting up their own software. Something that almost all software vendors provide.
The forum leaves a lot to be desired as well. Almost everybody is reluctant to put forth any information past the basic knowledge stuff because it might hurt their pocket book, when in fact there is plenty of business to go around. People are going to ask the same question over and over again, you are going to get very basic questions that seem pointless, it's an open forum and should not get frustrated. This is one of the main things I like about here There are a few there that are willing to help, don't get me wrong and they are very appreciated, but it's getting to the point to where people are trying to use it as their remote tuning platform. Which hinders knowledge sharing since a lot of people have bought it for the hobby/diy, not profit.
I ended up buying the tuning school guide for the GEN V, and it has answered a bunch of questions that I will be happy to share once I get a better handle on it.
OK Rant off..........
Last edited by Ghostnotes; 08-14-2018 at 11:28 AM.
I found that after the C7 hit the pavement, some aftermarket exhaust systems ( headers to cat back) did not want to develop mufflers because of the AFM Valves, but thanks to HP Tuners................and a couple more credits, there's a work around.
12-23-2017, 03:26 PM
HOW TO: Disable AFM Exhaust Valve Actuators with HP Tuners
