I know there are other threads dealing with similar issues but I thought since my codes are not the same and I didn't want to highjack anyone's thread here it goes.

A few weeks ago at Carlisle I had a Magnaflow Competition (M66-19173) axle back exhaust put on. I was sold when I was walking by the trailer a sales rep was revving one of the vettes they just installed one on up. The sound is just killer and I wanted it. Well I had it put on the same day and have loved every minute of it since.

The only issue I'm running into is that day as I was leaving Carlisle the engine light came on. Unfortunately at the time my schedule was so compressed with family obligations I could not come back for any troubleshooting or repairs. I have since opened a trouble ticket with Magnaflow.

I would like to ping all our vette mechanics and experts to provide their input and assistance so I can move forward with the pesky engine light blaring at me on the dash.

The codes:

P12E9
P12F6
P26C8

Through previous postings of similar errors with the Borla and Corsa axle backs and their recommendations I took it to the dealer last week to perform the AFE module recalibration service. I have also tried clearing the codes using an OBDII tool and both the dealer and tool gave the same results. After about the 3rd start-up the codes would come back. I read where the light will go away and the system will self correct after some time but I have since driven over 300 miles with that maddening engine light.

The car runs great, there are no drivability issues and all the valves work as they should as I am hearing the customary clinking sound with aftermarket axle backs with NPP when the car goes goes from 8 to 4 cylinders. My wife also verified the valves at the outside tips are working by visually watching them open and close while I switched the settings from Eco to Sport and back again.

Any experience, help, advice, anything to help move this along. I'm not really interested in having a custom tune installed to remove the light because I still have 2years on the factory warranty left.

Thankfully I had the VA State inspection done on the car before I went to Carlisle so I'm good for anther 11 months. Engine lights are auto fail for VA inspections as far as I have seen and been told.

Lastly just wanted to say after initially wanting to go with the Billy Boat exhaust I'm so glad I went with the Mangaflow because even thought the performance is only lightly noticeable the sound is absolutely incredible!

Thanks,
Eric

 

After some deep, intense, mind numbing thought I think I'm going to clear the codes and try the fuse #41 pull trick and see how that works out. It will be interesting what codes if they pop at all and if the ones that do are related to the cylinder management valves. I forget the acronym.

I'm at a loss as to what the codes mean because all my searches pull 'generic code' returns. At least this could separate which ones deal with the NPP and the cylinder management valves.

 

From everything I've read on axle back set-ups, is that they don't cause codes unless the AFM valves ahead of the mufflers are deleted or disconnected. Deleting the NPP valves or pulling the 41/42 fuse definitely doesn't cause codes.

 

I agree. The AFM actuators will throw CELs if they are disabled (fuse pull), unplugged, impeded in operation, or moved to a new exhaust system that has changed the "response" of the valves the actuator is trying to move.

The NPP actuators won't throw codes if disabled (fuse pull) or unplugged...BUT there are reports of CELs from the NPP actuators due to impeded/changed operation from valve malfunction/seize or from being moved onto a new exhaust since the valve response has been altered.

This typically requires the actuator re-learn that the OP has done...which makes this troubling. I'd make sure the dealer did the re-learn for BOTH AFM and NPP actuators.

From a physical check standpoint, I'd make sure all the actuators are installed properly and that all the wire harness plugs are properly installed/seated.

Clearing the codes and pulling the NPP fuse (41 or 42) to see if the CEL returns could eliminate them as the source. If it does clear permanently with the fuse pulled that means the valves in the tips are sticking/stiff, faulty actuator, or they were not re-calibrated property in the re-learn.

If the CEL comes back after the NPP fuse pull, then it's the AFM. From there it's a matter of figuring out whether it's a faulty valve, faulty actuator, needs another re-learn, etc.

As a last note, I do believe I recall a thread where the valves on an aftermarket exhaust were enough out of spec that the actuator re-learn never took. A replacement exhaust (since valves are welded in) fixed the issue.

 

Those codes are related to your exhaust. P12E9 - cylinder deactivation exhaust flow valve open position bank 1, P12F6 cylinder deactivation exhaust flow valve open position bank 2. P26C8 - chassis control module requested illumination. Emissions in VA are good for two years.
Last code is probably related to the first two.

 

Great info on the codes but the "cylinder deactivation exhaust flow valve" are the AFM actuators that are attached to the axle back the OP has from Magnaflow.

This essentially confirms it's the AFM actuator (or stuck/sticky valve), and more specifically it's whichever side "bank 2" is.

In the photo below, the AFM valves are ahead of the muffler, and the NP valves are in the exhaust tips.

 

Yes you are correct - fixed my post. Confused myself!

 

That is exactly the information I needed to know! Now I can move forward with Magnaflow.

 

Hey op can you elaborate on the magnaflow exhaust for us?

You are the first I have seen to state you have the competition series.

Maybe even a sound video?

Any drone?

Musclecar sound or not?

Etc.

Thanks and good luck on clearing the issue.

 

Sure, I have some video of the before and after at Carlisle. I'll post all that stuff under a different thread to keep this one aligned with the issues.

No real drone, and the sound is a mix between Muscle car and Super car, leaning more toward the super car sound though. I say this because of the stock cam there really isn't much lobe so the revs are smooth and fast.

Eric

 

thanks

 

I got those codes on my 15 when I pulled both fuses on my NPP, last year, I did it about a month after I had my car.

If the fuse is in, + the wires are on the codes will clear themselves, what they probably didn't do was plug the wires back into the valves.

 

Posted a new thread with vids:

https://www.corvetteforum.com/forums...k-exhaust.html

 

Yeah that was the first thing I checked. The dealer also checked them when they did the relearn. Everything is connected as it should. I'm wondering if the modules were banged or bumped during the installation or it could be the valve's them selves are just out of tolerance for the modules.

Still waiting to hear back from Magnaflow.

 

Having the same issue with mine on the akrapovic system. Seems it's the valve tolerance waiting for a reply from them as well..

 

Well 2nd startup and the CEL came on again, I guess this weekend while I wait for a response from Magnaflow on moving forward I'll jack up the rear end and triple check all the wiring.

 

There have been numerous reports of aftermarket C7 exhaust systems with AFM or NPP valve "response" characteristic issues that throw CELs.

The valves themselves are spring-loaded (closed), and the closed-loop control of the valves is VERY precise. Take a look at Theta's thread on the retrofit controller he built...and that will tell you how much is going on with these things. Any variance from OEM spec of the valve response from the expected calibrated response feeds back to the actuator and control system...and will likely CEL you.

So I suspect both you guys are victims of the valve response spec issue. It may be difficult or impossible to "fix" without a new exhaust system (since the valves are welded in). And a new exhaust may or may not have valves that are better.

Akrapovic does have their own controller that they engineered for retrofit purposes on non-NPP cars. Not sure of that could be a band-aid to get around the BCM.

 

Great news,

Just heard from a tech with Magnaflow they have replicated the problem and conducted a full redesign of the AFM valves. I'm assuming this will change the part number for the competition exhaust. They are also sending me a new kit once the production lines are keyed for the new valves.

Anxiously waiting by my mailbox!