767guy

Thanks for the info....yes 2015 only 17 months old so lots of warranty remaining. The more I listen to it the more I think it may be a bad valve in the pipe rather than the electric actuator. I think a bad actuator would have a bit of a squeak and sound dry. This thing sounds more like the noise you hear in the HVAC system as pneumatic valves open or close.Maybe the butterfly valve is misaligned and and rubbing or chaffing internally on the pipe. If that the case they will be dropping the exhaust to replace it...........after I have had the shop look at it I'll post the results.

ap6954

Well I think I just got bit with the dreaded AFM valve failure bug. After a weekend at the track got a CEL on the way home and ran the codes and it was the P12E7, P12E9, etc codes that are related to the valve failure. Cleared the CEL and it came right back. Car is making no noises as some have reported. It's off to the dealer Monday for a visit. My exhaust is wrapped all the way to the hump over the axle and I have the Z06 ducts and every other mod to try and keep temps down. I have tracked the car about 10 times and had no issue other than high auto trans temps. Hopefully this will not be a reoccurring thing. I am getting faster at the track so a permanent fix would be great If anyone has come up with one. Will see what the dealer says. I may be in the same boat as descartsfool and be trading in my C7 for something else if this is a reoccurring problem.

ap6954

Reference the post above. Dealer I brought it to is claiming it is not warranty to replace the failed actuators. Said looks like they have been tampered with. Exhaust has never been out of the car. I am Original owner. I said try again. Awaiting their response. Any advice?

raylo

Also wonder if this is another failure for us folks not tracking our cars to perhaps look forward to, but later in the game when warranty is gone....

Zajac

I am still thinking about these C7 AFM failures as I get my C7 Base ready for the upcoming track season at Miller Motorsport Track in Utah. I usually run a Supercharged 2007 Saleen Parnelli Jones Mustang for my track fun but I am thinking about the C7 for this season.

As an aside...the Saleen PJ Mustang is actually more track ready "out of the box" than the C7 as far as heat issues. Just change pads, fluids and tires.

Anyway, back to the C7 AFM issue......

1. too much heat at the AFM... DEI heat wrap slows heat transfer to the trans but may actually keep the heat inside the exhaust pipe at higher levels adjacent to the AFM shaft leading to subsequent AFM module failure.

I am just at home sick today and bored and thinking about this.....

2. Idea one....Add cooling air flow to the AFM actuator itself. Install air scoops (1" x 4''Wide" for example) under car and appropriate ducting to direct air flow up to each AFM.

2. Idea two.... Think out of the box......Must keep AFM shaft in stock location for proper ECU operation, etc. Okay. So leave just the AFM shaft itself in stock location and but no AFM actuator "guts". Install a separate AFM actuator and wiring connections in a remote but cooler location...say, somewhere precisely above the existing AFM location but in the hatch. Design a physical shaft extension from the original AFM shaft to the remote AFM shaft. All electrical signals to the remote AFM now physically control the original AFM shaft in the exhaust.

A little bit of "Rube Goldberg" fabrication is all that is needed. But the basic idea is to move the AFM module out of the heat zone but still controlling the actuator located in the exhaust.

Black Snake

Zero track time, these things are still failing...................

ap6954

Airflow across the actuators won't help. They are heating up through conductivity with the hot exhaust pipe. Not air temp. As far as re engineering the actuators I don't want to get into that. The car is under warranty and I should not have to chop it up to keep it from throwing a CEL. They have failed both with wrapped exhaust and bare. It's just a bad design that cannot be programmed out.

descartesfool

I find it sad and amazing actually that GM has not come up with a Technical Service Bulletin or equivalent since 2014 with a simple engineering fix for these AFM actuators that fail due to overheating caused by their direct connection to the exhaust pipe. How hard can it be for the engineering team to come up with a solution to permanently fix each one that fails with an improved part. Those guys aren't stupid. Must be a bean counter issue, but doesn't GM care about their customers????

Selling my Z51 this spring because GM is a total fail on this issue. So disappointed, but I've moved on. AMG GT-S is arriving April 25th. Can't wait!

and i will never buy a GM product again, and that C7 was my first one, and thus the last. I thought they had changed their ways since the bankruptcy....I was wrong.

RapidC84B

Doesn't the Z06 have AFM as well? If so, why no AFM valve on their catback?

descartesfool

Z06 has AFM but does not have AFM actuators before the muffler and thus does not restrict the exhaust flow like they do on the non-Z06 models. AFM actuators are there to change the sound to a less objectionable tone when AFM is on. I can only assume that they knew they would fail even more rapidly on the Z06 with its 650 HP motor and more heat energy into the exhaust, so they decided the noise quality was less important than failing AFM actuators.


When I took my buddie's Z06 to my dealer to show them it had no AFM actuators, they were surprised when they looked under it. When I asked for a trade-up to a Z06 for my failing Z51 since they had no GM fix for it, they said they did not want to sell me one as they knew that if I was overheating engine and manual transmission on my Z51 and also having AFM actuator failures on track that I would also likely overheat a Z06, since they knew of overheating issues on the Z06 per their contacts with the GM Camaro and Corvette brand quality manager. Hence why I have given up on Corvette. I contacted every possible person from GM that might help in terms of a fix and not a single one ever responded. After 5 sets of AFM actuator replacements, all I can say is my car is a pain in the ***. Great on the street, but it can't take the heat on the track when driven hard core.

RapidC84B

Interesting that GM just ditched the valve on the Z06 and accepted the odd sound in V4 mode. I mean I get it.... as you said it'd die in short order with the Z06 Hellpig.

ap6954

Reference posts #82 and #83. After long discussions with my dealer they fixed the AFM problem. It was not a melted actuator. I showed them pictures of a melted actuator and mine did not have this. Said the wiring harness on the driver side AFM plug wiring pin connectors were backed out of the plug. Weird. The plug has never been messed with and I am the original owner. They did replace the actuator though since when they tested it with the laptop it was a little "jerky". Problem solved. I'll see if the problem returns.

Tomljanovich

What are the AFM actuators??? Define acronym first time you use it! This is for all new C7 owners.
Thanks.

Suns_PSD

Whenever you track a car at a high level you always find weaknesses, after all it's not a race car.
Why after the second failure you didn't just make the necessary aftermarket parts upgrades to remove the weak link is beyond me. Would have been easier and cheaper than getting rid of the car.
Good luck.

RapidC84B

Because GM markets the car as being able to handle a basic 20-30 minute HPDE session.

Tomljanovich

HPDE?? High Performance Driving Experience??

RapidC84B

High Performance Driving Event aka a trackday.

Suns_PSD

It is certainly a high level sports car but no car can withstand every high performance scenario.

The OP is clearly experienced, drives at a high level, and really should know this.

My '08 Z51 is overheating brakes at the track, even with full Z06 aftermarket rotors, calipers, race fluid, SS lines, and pads. If I drive it just a little slower there is no problem, but to run at my 90% pace the brakes are done in just 2-3 laps. So now I am improving brake cooling and that will give me a bit more to play with, but then it'll just go to the next weak link. It's a 3K# car that makes 500 rwhp driven at a reasonably high level, it's to be expected.

No matter what GM builds a better driver can make it overheat/ break/ flex/ etc... Do you have any idea what a real race car costs that doesn't even have to compromise to be road legal and comfortable? 6-20x what a new Vette cost.

The OP might end up with a better track day car, but it will certainly make compromises in either streetability and/ or cost. A nice dialed Vette will run with any other street car at the track and you can still take your wife to dinner in style that evening!

descartesfool

There is currently no possible way to fix this issue with any kind of aftermarket part. If there was, I would have fixed it. So while it is beyond you, it is also beyond GM and the entire aftermarket industry.

Here is why: the CCM (Chassis Control Module) that controls the AFM actuator (Active Fuel Management or simply the V4 mode) tests the operation of the AFM actuators each and every single time you power up the engine. It moves the actuator to the closed position and gets a feedback signal from the rotated actuator that it has reached the closed position and then returns it back to the normal open position. If the actuator or valve it controls does not move and then return the actuator and valve via the return spring action on the valve, you get a CEL (Check Engine Light) on the dash display. So if you remove the actuator, disconnect it or do anything else, the CCM will detect a fail at startup and then you have a permanent CEL, meaning you have no idea if you have more than one issue causing a CEL. While it is possible to do a warranty voiding engine tune that will disable the AFM activation, these tunes do not stop the test upon startup, so nothing to do with tuning modules.

No one has figured out to hack the CCM module which is what is required to fix this issue with an aftermarket part, and no one has made a different AFM actuator that does not fail with the heat it gets when the car is driven really fast on track.

If anyone has ever heard of a way to fix this, post it up, as no person from GM has ever responded about a fix, including both guys I spoke to at the GMPP booths at SEMA in 2014 and 2015, nor the tech contact that Spring Mountain Ranch uses for their technical issues with the Vettes, Jeff Strausser, nor the GM Camaro and Brand Quality manager who was looking after my case, Jennifer.

Chets LS3

so essentially a tune won't fix the CEL issue either? through the computer can you demand the computer to not throw a light with specific codes thrown (IE the afm codes)