When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
AFM actuators have failed again on track for my Z51
Second time I have run my Z51 on track, and second time the AFM actuators have failed. 2 for 2. I got an engine check light, took it to the dealer, and he confirmed it was the same failure as last time I had it on track.
So, 2 track days, 2 failures of the AFM actuators. My car is 2014 C7 Z51 M7 with MRC, running in Track mode, PTM set to Sport 2. Less than 1.5 hours of track driving this time, and they actually failed halfway when I got the CEL.
So who else has had their actuators fail? Ron Fellows school manager told me last year they were having the same issue and that GM knew about it. Dealer checked and there is no new part number since the last ones they replaced.
Anyone know of a solution? Car checks the position/actuation of the actuator every start-up, regardless of what mode you are in. Dealer says mine are in the stuck open position, and until they get replaced, CEL will stay on. So just taking them out is not really an option.
I unbolted the actuators, got a bunch of washers from Home Depot to create a heat sink and longer bolts to account for the washers. I stacked about 4-6 washers (cannot remember since I did this a couple years ago) per bolt. It creates enough gap where the actuator is able to be bolted to the exhaust but the valve doesn't actually make contact, basically making it non functional. However (knock on wood), I've been running for over two years now like this with over 1k track miles and zero failures or issues since.
Shop foreman was very sympathetic and printed out the circuit diagram for me of the exhaust wiring and we looked it over together. The AFM and NPP actuators are wired differently. Both have a power signal to pin 4 and ground to pin 1, plus an actuation signal. The actuation signal is common to both NPP and AFM actuators on pin 2, but for the AFM ones, there is a separate feedback signal from pin 3 that goes back to the ECU, one per actuator. There is no such feedback wiring to the ECU from the NPP actuators. Diagram shows a link connection on the NPP ones between pins 3 and 5. There is no pin 5 shown on the AFM actuator in the diagram.
I can't see them failing again on my next track day, and having to go to dealer every single time I take the car to the track. I see there is a fuse for the NPP actuators and another one for the AFM actuators, so obviously they are easy to power down, but that won't do anything for the feedback signal and the ECU error when it doesn't see the correct feedback when powering the valves.
I e-mailed the manager of the Ron Fellows school at Spring Mountain today and he was again nice enough to e-mail me back because he had told me last year they were also having failures of the AFM actuators like I am. I asked him if they had a fix because he had told me GM knows about the issue. He said there was no fix or improved part that he knows of, and that they had reduced failures by implementing a good cool-down lap. But that is for newbie students driving usually for the first time on track and who are not pushing the car at full tilt for 30 minutes steady per session like I am. Based on his recommendation last year, I did a cool down lap after my first session last weekend and even drove off track to fill up with gas, but when I started the car up after the fill-up, CEL showed up and that was due to an actuator fail.
Really need a fix for this. Some way to remove valves without throwing a CEL. Perhaps cut out a spring loaded AFM valve off a muffler and mount the actuator and valve off the exhaust and just have it move without actually being in the exhaust flow. Sounds like a big pain.
Just got my failure number 3 of the AFM actuators, in 3 track days. Picked up the car from the dealer on Thursday after they replaced both AFM actuators, and shop foreman wanted me to get it back to the track as soon as possible to see what would happen. He said he had no confidence it wouldn't happen again like both other times. So yesterday I go to the track, it's 72 degrees out. I run for 30 minutes at speed, and pull into the paddock. When I go to start the car, I get a CEL on the dash as before due to CCM checking the actuators at every startup, plus noise from rear as actuators are trying to go through their test. So it's back to the dealer once again for the same repair. I opened a case with GM Customer Care after I picked up the car from the dealer per the shop foreman's suggestion. I have no idea where it's going to go from here, but it's obvious GM needs to re-design those actuators. The shop foreman took some pictures of the actuators which show evidence of overheating where the actuator's plastic case mount to the exhaust pipe mounted valve. These valves were brand new with 1 session on track failure. Dealer says he is shipping the broken actuators back to GM. Perhaps he could wait until he replaces the ones he just put on the car and save some postage!
1st of the 2 failed actuators, with melting near the metal circular rotating piece.
Now that's interesting - thanks for posting those pictures. Have not seen external heat damage to these until now (outside of testing), but it gives me a good idea of where contact is being made.
That's enough heat to destroy the small motor sitting less than 2cm away from those marks. The scorch point of the plastic is actually quite high, and the melt temp was ~350C in testing. The butterfly arm is supposed to be thermally isolated from the exhaust, which is ludicrous, as it's still connected to the actual butterfly in the exhaust path.
There's a reason they removed these from the Z06, and it's beginning to become clear.
Now that's interesting - thanks for posting those pictures. Have not seen external heat damage to these until now (outside of testing), but it gives me a good idea of where contact is being made.
That's enough heat to destroy the small motor sitting less than 2cm away from those marks. The scorch point of the plastic is actually quite high, and the melt temp was ~350C in testing. The butterfly arm is supposed to be thermally isolated from the exhaust, which is ludicrous, as it's still connected to the actual butterfly in the exhaust path.
There's a reason they removed these from the Z06, and it's beginning to become clear.
My friend's Z06 I looked at on my lift had no AFM valves. When we took the Z06 to have the shop foreman confirm with his own eyes that there are no AFM valves on the Z06, he forwarded that info to the GM Quality manager for Corvette and Camaro he as been communicating with. She then asked for the VIN of the Z06 he had looked at to confirm. She called him back and said info she found per the VIN indicated there are AFM valves on that Z06, and shop foreman checked on his computer and it only showed that all C7's have AFM actuators, when they clearly do not. I saw his info myself on his computer in his office. So there is certainly some mis-information in the official GM documentation that has been looked at by both my shop foreman and the Quality person he has been communicating with.
Really not sure what to do at this stage. Every 30 minutes on track these things are failing, and since CCM checks for proper operation at each startup and throws a code if they aren't working, there seems like no solution until GM re-engineers the part or mounting. It's a conundrum. Repair is quite expensive for every track day, and much more costly than the track day itself. What will GM do, as it's an absolute defect in design, and they are going to have to pay for the warranty repair every single time I take it to the track?????
My friend's Z06 I looked at on my lift had no AFM valves. When we took the Z06 to have the shop foreman confirm with his own eyes that there are no AFM valves on the Z06, he forwarded that info to the GM Quality manager for Corvette and Camaro he as been communicating with. She then asked for the VIN of the Z06 he had looked at to confirm. She called him back and said info she found per the VIN indicated there are AFM valves on that Z06, and shop foreman checked on his computer and it only showed that all C7's have AFM actuators, when they clearly do not. I saw his info myself on his computer in his office. So there is certainly some mis-information in the official GM documentation that has been looked at by both my shop foreman and the Quality person he has been communicating with.
Really not sure what to do at this stage. Every 30 minutes on track these things are failing, and since CCM checks for proper operation at each startup and throws a code if they aren't working, there seems like no solution until GM re-engineers the part or mounting. It's a conundrum. Repair is quite expensive for every track day, and much more costly than the track day itself. What will GM do, as it's an absolute defect in design, and they are going to have to pay for the warranty repair every single time I take it to the track?????
You could remove the actuators to allow the valves to remain always open and then have your tuner tune out the codes for you.. Just a thought..
You could remove the actuators to allow the valves to remain always open and then have your tuner tune out the codes for you.. Just a thought..
Ant
If it was just that simple!
Chassis Control Module checks the operation of the AFM actuators every time you turn on the car, regardless of what mode it's in. There is a spring in the valve which is mounted in the exhaust pipe that helps resist motion of the actuator and returns the valve to full open if the actuator is un-powered or not active. The AFM actuator unlike the NPP one is set to only partially open when activated (otherwise it would totally block the exhaust pipe), and there is a feedback wire back to the CCM computer that tells it that the valve is in the correct position on test or in ECO mode. So if you remove the actuator, even without disconnecting the cable, the car will throw a CEL the first time you turn the car on, and it will never clear. Then if there is something else wrong with the car, you won't know because the CEL is already on. And there is no possible way to change the software so the CCM doesn't check the operation of the valve on startup AFAIK. And I don't have a tuner, car is totally stock.
This is an improper design by the GM team, putting a plastic cased electronic module directly on the exhaust pipe. Just bound to fail when the going gets hot. Actuators are expensive with a list price of almost $400 each, so it's well over $1000 to repair each time at the dealer for every one of my track outings. So far it's covered under warranty, but this can't really continue. If GM doesn't come up with a fix, I might have to sell the car. I bought it to go to the track and for now it fails every time I go.
Chassis Control Module checks the operation of the AFM actuators every time you turn on the car, regardless of what mode it's in. There is a spring in the valve which is mounted in the exhaust pipe that helps resist motion of the actuator and returns the valve to full open if the actuator is un-powered or not active. The AFM actuator unlike the NPP one is set to only partially open when activated (otherwise it would totally block the exhaust pipe), and there is a feedback wire back to the CCM computer that tells it that the valve is in the correct position on test or in ECO mode. So if you remove the actuator, even without disconnecting the cable, the car will throw a CEL the first time you turn the car on, and it will never clear. Then if there is something else wrong with the car, you won't know because the CEL is already on. And there is no possible way to change the software so the CCM doesn't check the operation of the valve on startup AFAIK. And I don't have a tuner, car is totally stock.
This is an improper design by the GM team, putting a plastic cased electronic module directly on the exhaust pipe. Just bound to fail when the going gets hot. Actuators are expensive with a list price of almost $400 each, so it's well over $1000 to repair each time at the dealer for every one of my track outings. So far it's covered under warranty, but this can't really continue. If GM doesn't come up with a fix, I might have to sell the car. I bought it to go to the track and for now it fails every time I go.
By tuning it out what I mean is that if you had your car tuned, the tuner can shut off certain CEL codes at will and can just shut off that specific code so it does not alert. Example is my long tube headers throw codes but I had him turn off those codes in the tune. The o2 sensors are not disabled and still work, but the code for the sensor receiving an improper A/F reading is ignored..
My friend's Z06 I looked at on my lift had no AFM valves. When we took the Z06 to have the shop foreman confirm with his own eyes that there are no AFM valves on the Z06, he forwarded that info to the GM Quality manager for Corvette and Camaro he as been communicating with. She then asked for the VIN of the Z06 he had looked at to confirm. She called him back and said info she found per the VIN indicated there are AFM valves on that Z06, and shop foreman checked on his computer and it only showed that all C7's have AFM actuators, when they clearly do not. I saw his info myself on his computer in his office. So there is certainly some mis-information in the official GM documentation that has been looked at by both my shop foreman and the Quality person he has been communicating with.
Really not sure what to do at this stage. Every 30 minutes on track these things are failing, and since CCM checks for proper operation at each startup and throws a code if they aren't working, there seems like no solution until GM re-engineers the part or mounting. It's a conundrum. Repair is quite expensive for every track day, and much more costly than the track day itself. What will GM do, as it's an absolute defect in design, and they are going to have to pay for the warranty repair every single time I take it to the track?????
Isn't that funny that the systems show that? Sadly, some of the first-batch Z06s actually have AFM valves. Poor guys...
CCM doesn't work like that, unfortunately, and it can't be touched with current coding/tuning.
There are maybe 2 (?) of us on here who know how to access and manipulate the CCM using analog means (which frankly isn't good enough). After spending a week looking into this problem and attempting to produce a feedback signal that would keep the MIL from popping up, I realized it was a lost cause.
Originally Posted by descartesfool
If it was just that simple!
Chassis Control Module checks the operation of the AFM actuators every time you turn on the car, regardless of what mode it's in. There is a spring in the valve which is mounted in the exhaust pipe that helps resist motion of the actuator and returns the valve to full open if the actuator is un-powered or not active. The AFM actuator unlike the NPP one is set to only partially open when activated (otherwise it would totally block the exhaust pipe), and there is a feedback wire back to the CCM computer that tells it that the valve is in the correct position on test or in ECO mode. So if you remove the actuator, even without disconnecting the cable, the car will throw a CEL the first time you turn the car on, and it will never clear. Then if there is something else wrong with the car, you won't know because the CEL is already on. And there is no possible way to change the software so the CCM doesn't check the operation of the valve on startup AFAIK. And I don't have a tuner, car is totally stock.
This is an improper design by the GM team, putting a plastic cased electronic module directly on the exhaust pipe. Just bound to fail when the going gets hot. Actuators are expensive with a list price of almost $400 each, so it's well over $1000 to repair each time at the dealer for every one of my track outings. So far it's covered under warranty, but this can't really continue. If GM doesn't come up with a fix, I might have to sell the car. I bought it to go to the track and for now it fails every time I go.
I had assumed you were untuned/stock, which is why they're continuing to replace these over and over for you. I'm wondering if they'll eventually raise an abuse flag (even though in my opinion, tracking a car sold under the auspice of being a great track car doesn't equal abuse), or at least look into the dealer service. Hopefully, those are being sent back to review. I'd love to be able to give my findings to a few key engineers there. Using your valves and my findings, we could most likely get this fixed. Problem is, though, that the cost of a widespread replacement like this could cost millions in parts and labor. Since you're one of perhaps 400 total owners that track the C7, they may just decide it's easier to keep replacing your valves. If this is the case, perhaps we can devise a type of heat shielding for that area to overlay before bolting the actuator onto the valve.
Originally Posted by descartesfool
My friend's Z06 I looked at on my lift had no AFM valves. When we took the Z06 to have the shop foreman confirm with his own eyes that there are no AFM valves on the Z06, he forwarded that info to the GM Quality manager for Corvette and Camaro he as been communicating with. She then asked for the VIN of the Z06 he had looked at to confirm. She called him back and said info she found per the VIN indicated there are AFM valves on that Z06, and shop foreman checked on his computer and it only showed that all C7's have AFM actuators, when they clearly do not. I saw his info myself on his computer in his office. So there is certainly some mis-information in the official GM documentation that has been looked at by both my shop foreman and the Quality person he has been communicating with.
Really not sure what to do at this stage. Every 30 minutes on track these things are failing, and since CCM checks for proper operation at each startup and throws a code if they aren't working, there seems like no solution until GM re-engineers the part or mounting. It's a conundrum. Repair is quite expensive for every track day, and much more costly than the track day itself. What will GM do, as it's an absolute defect in design, and they are going to have to pay for the warranty repair every single time I take it to the track?????
Isn't that funny that the systems show that? Sadly, some of the first-batch Z06s actually have AFM valves. Poor guys...
The Z06 CCM must be different from either a physical aspect or a simple coding aspect to eliminate the checks for the AFM valves. I'm wondering if a combination of GDS2 and SPS can force a flash of a Z06 CCM opcode onto a normal C7 part. I will look further into this. To make it work, though, I would need both a donor C7Z, and the recipient C7 lined up next to one another, and then essentially do a dirty flash... Sounds like a dead CCM to me, but I'll work at this and see if I can come up with something.
That will rid you of your problems for good. I plan to do this for my own benefit, as Id like to run a Borla Z06 system with no AFM butterfly.
Originally Posted by FYREANT
By tuning it out what I mean is that if you had your car tuned, the tuner can shut off certain CEL codes at will and can just shut off that specific code so it does not alert. Example is my long tube headers throw codes but I had him turn off those codes in the tune. The o2 sensors are not disabled and still work, but the code for the sensor receiving an improper A/F reading is ignored..
It's a valid point you have, but unfortunately for us, the CCM doesn't work like that. It can't be touched with current coding/tuning.
We also can't leave the valves dangling and connected as the 'torque applied' calibration will fail upon boot/startup.
There are maybe 2 (?) of us on here who know how to access and manipulate the CCM using analog means (which frankly isn't good enough). After spending a week looking into this problem and attempting to produce a feedback signal that would keep the MIL from popping up, I realized it was a lost cause.
It's a valid point you have, but unfortunately for us, the CCM doesn't work like that. It can't be touched with current coding/tuning.
We also can't leave the valves dangling and connected as the 'torque applied' calibration will fail upon boot/startup.
There are maybe 2 (?) of us on here who know how to access and manipulate the CCM using analog means (which frankly isn't good enough). After spending a week looking into this problem and attempting to produce a feedback signal that would keep the MIL from popping up, I realized it was a lost cause.
Why am I not surprised . And here I thought I had a simple idea that would work only for it to fall on its face due to the engineers at GM and the stupid complexity of a simple system.. LOL
The solution I have thought of is to have some actual AFM valve sections not part of the exhaust installed in the area of the actual AFM valves and connect the actuators to them and leave them connected to the CCM. That way there is a spring on the additional (or cut-out) AFM valve that the AFM actuator works against, and when the CCM sends a signal to the AFM valves, they move just as if they were mounted on valves actually in the exhaust, and the CCM can't tell the difference. Since the AFM actuators would not be touching the actual exhaust pipe, they wouldn't melt and fail.
I would have to know where to buy just the AFM valve sections with the springs. Not a super elegant solution, but it should work. Of course the proper thing is for GM to fix their defective design. As I have posted before, I got confirmation that the Z51's at the Ron Fellows school are having the same issue when driven hard on track, and that they had advised GM a year ago about this. Z51 is after all the track pack for the C7. It can't be rocket science for GM engineering to come up with a properly functioning design. Since they removed them from the Z06, they knew it was a failure of engineering design on the original Z51. But new 2015 Z51 at the dealer has the AFM valves along with the NPP valves.
My buddy with his Viper T/A has had zero overheating or failure issues of any kind for well over a year of tracking his car. I was at VIR with him last June in high heat and it ran flawlessly. If Viper can be properly engineered not to overheat with 640 HP when run hard on track, surely GM can do the same.
The solution I have thought of is to have some actual AFM valve sections not part of the exhaust installed in the area of the actual AFM valves and connect the actuators to them and leave them connected to the CCM. That way there is a spring on the additional (or cut-out) AFM valve that the AFM actuator works against, and when the CCM sends a signal to the AFM valves, they move just as if they were mounted on valves actually in the exhaust, and the CCM can't tell the difference. Since the AFM actuators would not be touching the actual exhaust pipe, they wouldn't melt and fail.
I wanted to do this for calibration, but there are only two options:
1) Cut apart an OEM exhaust for the two spring assemblies, or
2) Contact an aftermarket exhaust company like Borla that makes their own spring assembly separate from the exhaust piping.
Took car into dealer once again this morning. Shop foreman hooked up his laptop to my car and confirmed both AFM actuators have failed once again. Took 30 minutes of track time.. There was also another code for my manual transmission overheating. AFM modules are on order.
GM Customer care actually called me at home this morning to find out how my track day went as they had called the shop foreman this morning to find out about the repair last Thursday, which really surprised me. I told her about what had happened on Friday at the track, and that I was just on the way to see the dealer. I live in hope that GM will come up with a fix.
Took car into dealer once again this morning. Shop foreman hooked up his laptop to my car and confirmed both AFM actuators have failed once again. Took 30 minutes of track time.. There was also another code for my manual transmission overheating. AFM modules are on order.
GM Customer care actually called me at home this morning to find out how my track day went as they had called the shop foreman this morning to find out about the repair last Thursday, which really surprised me. I told her about what had happened on Friday at the track, and that I was just on the way to see the dealer. I live in hope that GM will come up with a fix.
I can, with near-certainty, tell you that this has now been flagged into the regional/national claims team systems. The third replacement of a failed item requires a mandatory inspection of the failed parts, and of your car specifically.
I'm very glad you are stock, as this is the only way you're going to be able to get someone to listen. I've tried to make inroads on this matter for months now with zero success.
Let's keep our fingers crossed that this can be addressed. The 'fix' is a little harder than it would appear, but it's doable. First, the AFM valves can be made of Delrin and then treated with heat reflective material. The shaft of the motor needs to be reworked with larger leads to absorb that much heat, and the bearings/lube need to be replaced with a larger motor with a high-temp grease.
Being at an oil company, we took a look at this early on and between being an EE and having a lot of CLS and knowledgeable chemists and lube specialists here, it was pretty apparent an overheat would cause catastrophic failure.
I'll probably get in trouble for even saying this stuff as usual...
06-03-2015, 01:59 PM
AFM actuators have failed again on track for my Z51
