Engine Code P12F7 Advice
Thread Starter
Racer
Joined: Apr 2017
Posts: 251
Likes: 215
Engine Code P12F7 Advice
Check engine light popped on today on my C8 with performance exhaust. Drove right home and parked and called OnStar. They had some trouble getting the code at first, but after shutting down and leaving the door open for 3 minutes they got it.
Came up as P12F7 - An issue has been detected with the exhaust tailpipe flow control system. This system is used to tune and control the exhaust note for vehicles. If the vehicle is continually driven with this light on the operator will experience exhaust sound performance degradation and abnormal vibration generated from the exhaust system.
It was swapping between V4 and V8 mode like normal on the way home and when I switched between exhaust mode there was an obvious audible change like normal.
I'll get it into service, but how safe is it to drive in the meantime. Can't really find others posting about this code ever being made, especially about a C8. Everything seems normal, but the idea of extra vibrations in the exhaust make me a little worried I could do damage.
Came up as P12F7 - An issue has been detected with the exhaust tailpipe flow control system. This system is used to tune and control the exhaust note for vehicles. If the vehicle is continually driven with this light on the operator will experience exhaust sound performance degradation and abnormal vibration generated from the exhaust system.
It was swapping between V4 and V8 mode like normal on the way home and when I switched between exhaust mode there was an obvious audible change like normal.
I'll get it into service, but how safe is it to drive in the meantime. Can't really find others posting about this code ever being made, especially about a C8. Everything seems normal, but the idea of extra vibrations in the exhaust make me a little worried I could do damage.
Race Director
Joined: Mar 2007
Posts: 11,096
Likes: 8,253
Check engine light popped on today on my C8 with performance exhaust. Drove right home and parked and called OnStar. They had some trouble getting the code at first, but after shutting down and leaving the door open for 3 minutes they got it.
Came up as P12F7 - An issue has been detected with the exhaust tailpipe flow control system. This system is used to tune and control the exhaust note for vehicles. If the vehicle is continually driven with this light on the operator will experience exhaust sound performance degradation and abnormal vibration generated from the exhaust system.
It was swapping between V4 and V8 mode like normal on the way home and when I switched between exhaust mode there was an obvious audible change like normal.
I'll get it into service, but how safe is it to drive in the meantime. Can't really find others posting about this code ever being made, especially about a C8. Everything seems normal, but the idea of extra vibrations in the exhaust make me a little worried I could do damage.
Came up as P12F7 - An issue has been detected with the exhaust tailpipe flow control system. This system is used to tune and control the exhaust note for vehicles. If the vehicle is continually driven with this light on the operator will experience exhaust sound performance degradation and abnormal vibration generated from the exhaust system.
It was swapping between V4 and V8 mode like normal on the way home and when I switched between exhaust mode there was an obvious audible change like normal.
I'll get it into service, but how safe is it to drive in the meantime. Can't really find others posting about this code ever being made, especially about a C8. Everything seems normal, but the idea of extra vibrations in the exhaust make me a little worried I could do damage.
Tech Contributor
Joined: Oct 1999
Posts: 40,995
Likes: 9,759
From: Charlotte, NC (formerly Endicott, NY)
If you don't have a state vehicle inspection coming up disconnect the battery and see if the code goes away. Then drive the car for a few days to see if it comes back. If it does I suspect it won't hurt to drive the car to the dealership as it is designed to be driveable on the street/highway with all exhaust valves closed.
Bill
Bill
Melting Slicks
Joined: Apr 2021
Posts: 2,741
Likes: 2,304
From: Simi Valley, CA
2022 C8 of the Year Finalist - Modified
I wouldn't worry about driving it. Even if a valve is stuck open or closed it won't do any damage (although if closed I wouldn't advise any wide open throttle or redline operation). If everything seems normal just get the CEL cleared and see if it comes back again. If it does come back, it might just need a valve relearn, which the dealer can easily do. In any case, it won't hurt the car to drive it until you find out what the problem is.
Thread Starter
Racer
Joined: Apr 2017
Posts: 251
Likes: 215
I had planned to disconnect the battery the next day, but I went out and started the car later that night and the CEL was gone. Drove it around for a few miles and it didn't come back. Hopefully it was just a fluke and it doesn't come back.
Supporting Vendor
Joined: Mar 2020
Posts: 712
Likes: 530
From: Atlanta, GA
You are perfectly fine to drive the car just fyi even if the code is on.
I know you said it has performance exhaust, do you mean the factory performance exhaust or something aftermarket?
Thanks
Andrew
Racer
Joined: Mar 2003
Posts: 277
Likes: 4
From: Halfmoon New York
Same code-GM Borla Exhaust installed
Sorry to hijack this thread but I'm having the same issue. Dealer diag said pretty much the same as is written here (valve issue) but they didn't have a solution except to have it either tuned out or don't worry about it. I'm concerned about both of those suggestions especially since its a GM purchased part that they installed and I can't imagine that either of those are a good course of action. Besides the expected "bring it to the dealer and insist they fix it" has anyone else seen this besides the OP and can give me some ammo/background to use when I chat with them again? As always, thanks in advance
Thread Starter
Racer
Joined: Apr 2017
Posts: 251
Likes: 215
Sorry to hijack this thread but I'm having the same issue. Dealer diag said pretty much the same as is written here (valve issue) but they didn't have a solution except to have it either tuned out or don't worry about it. I'm concerned about both of those suggestions especially since its a GM purchased part that they installed and I can't imagine that either of those are a good course of action. Besides the expected "bring it to the dealer and insist they fix it" has anyone else seen this besides the OP and can give me some ammo/background to use when I chat with them again? As always, thanks in advance
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Thread Starter
Racer
Joined: Apr 2017
Posts: 251
Likes: 215
I never saw this comment, sorry for not responding to your question. It's the factory performance exhaust. I would have been less concerned if it was an aftermarket setup.
Racer
Joined: Mar 2003
Posts: 277
Likes: 4
From: Halfmoon New York
or I wonder if state inspection will also be an issue? Its frustrating that this is a GM part that a dealer installed. Seems to me this should be fixable but what do I know. I'm just a squirrel looking for a nut.
Race Director
Joined: Mar 2007
Posts: 11,096
Likes: 8,253
Sorry to hijack this thread but I'm having the same issue. Dealer diag said pretty much the same as is written here (valve issue) but they didn't have a solution except to have it either tuned out or don't worry about it. I'm concerned about both of those suggestions especially since its a GM purchased part that they installed and I can't imagine that either of those are a good course of action. Besides the expected "bring it to the dealer and insist they fix it" has anyone else seen this besides the OP and can give me some ammo/background to use when I chat with them again? As always, thanks in advance
Racer
Joined: Mar 2003
Posts: 277
Likes: 4
From: Halfmoon New York
What does "tuned out" mean? There are procedures that should be performed any time the AFM and tailpipe flow control valves or actuators are messed with. They are "Cylinder Deactivation Exhaust Control Valve Learn." and "Exhaust Control Valve Learn". The first one addresses the AFM valves that are just after the cats at the muffler inlet and the second one addresses the valves in the tailpipe that control the exhaust loudness. If that does not correct the problem - then DTCs point directly to one or more diagnostic procedures for tracking down the problem. Think of it as pointing to the general area where a problem exists. Then by following the indicated diagnostic steps, the tech can pinpoint the issue. And it could be a pinched wire, a damaged actuator, a problem with the valve on the muffler, failure to perform the learn procedure, or something else. Did your dealer perform those diagnostics? If a dealer follows the diagnostics and is unable to solve the problem, they are then supposed to contact GM for engineering help.
I did email the service manager yesterday with the GM bulletin on the relearn procedure and asked if that was done. I await their reply. Your further info is great and much appreciated! I'll call them today if I don't hear back and ask when they want me to bring it in. They are decent folks, I just think they haven't done this kind of stuff before and were a little to dismissive.