Active Fuel Management Issues / Question

ElJefeBlanco · December 1, 2017

14 hours ago, KARNUT said:

GM has a factory performance exhaust upgrade, maybe you could get them to do that instead of stock replacement.

Sent from my iPhone using Tapatalk

That's a good idea. I wish I would have thought of it myself. I'll mention it to them and see how it goes.

Sierra706 · December 1, 2017

Would switching to an aftermarket exhaust eliminate the problem?

Gets rid of the squeak. But most aftermarket exhausts are louder and when in V4 mode your truck sounds terrible.

Sent from my iPhone using Tapatalk

EFLine · December 1, 2017

10 hours ago, ElJefeBlanco said:

Would switching to an aftermarket exhaust eliminate the problem?

yep! as long as the new system does not have the flapper valve. I think also deactivating AFM would solve this too. Heck just get a tune from BB and exhaust

harrisonhunter · December 2, 2017

yep! as long as the new system does not have the flapper valve. I think also deactivating AFM would solve this too. Heck just get a tune from BB and exhaust [emoji4]

My 2017 have the exhaust replaced at a 1000 miles. The flapper was I believe in the front of the muffler and the new exhaust has the flapper in the back of the muffler. And this one has been quiet for 16000

Sent from my SAMSUNG-SM-G930A using Tapatalk

ElJefeBlanco · December 2, 2017

16 hours ago, EFLine said:

yep! as long as the new system does not have the flapper valve. I think also deactivating AFM would solve this too. Heck just get a tune from BB and exhaust

I plan on deactivating the AFM soon. I read on here that HyperTech has a tuning kit where you can adjust it to not come on until a preset MPH.

ElJefeBlanco · December 2, 2017

6 hours ago, harrisonhunter said:

My 2017 have the exhaust replaced at a 1000 miles. The flapper was I believe in the front of the muffler and the new exhaust has the flapper in the back of the muffler. And this one has been quiet for 16000

Sent from my SAMSUNG-SM-G930A using Tapatalk

I'm going to have to pay attention to where it is on the new one that they ordered once it comes in.

Bowtieguy17 · December 4, 2017

I have the 2017 Z71 5.3 and did the K&N CAI, Magna-flo exhaust, and the Diablo Predator 2 Tuner. I disabled the AFM and it works great now. I was tired of the low rumble and the constant switching from 4 to 8. Plus, there's been many problem with burnt out cylinders as a result of the AFM and I'm not willing to take that chance. My fuel mileage (on 87 economy) is about 375 miles per tank.

Grumpy Bear · December 4, 2017

26 minutes ago, Bowtieguy17 said:

I have the 2017 Z71 5.3 and did the K&N CAI, Magna-flo exhaust, and the Diablo Predator 2 Tuner. I disabled the AFM and it works great now. I was tired of the low rumble and the constant switching from 4 to 8. Plus, there's been many problem with burnt out cylinders as a result of the AFM and I'm not willing to take that chance. My fuel mileage (on 87 economy) is about 375 miles per tank.

I keep hearing members saying this happens and yet I haven't heard a single case reported by any member personally in the Ecotec3 platform. Over 158,000 members and not a single case that can be traced to the AFM? I'm starting to smell skunk butt.

Bowtieguy17 · December 4, 2017

34 minutes ago, Grumpy Bear said:

I keep hearing members saying this happens and yet I haven't heard a single case reported by any member personally in the Ecotec3 platform. Over 158,000 members and not a single case that can be traced to the AFM? I'm starting to smell skunk butt.

I have two friends who own 14s and both have problems with burnt cylinders and lifters. I'm not taking the chance.

94boosted · November 21, 2018

On 11/29/2017 at 6:46 PM, n1ghtsh1ft said:

I took my '17 Sierra in for the same thing today. After doing a bit of digging online, I referenced PIT5404D (Dated June 16, 2017) and the techs were able to reproduce the squeak and verify that PIT5404D was the correct bulletin. I'm in Canada, it will take a week or two to get whatever parts necessary to fix it.

I had the entire exhaust system replaced under warranty on my 2015 5.3 at 27K miles, 14 months later and now at 38K miles the noise is back. Take it to my dealership and they refuse to replace it, worst part is my comprehensive warranty expired 3 days ago. Such an awful dealership. What are my options? Is there any way to force the valve to stay open? Or if I get some sort of a piggy back tuner that disables AFM does the valve permanently stay open?

n1ghtsh1ft · December 4, 2018

On 11/20/2018 at 5:43 PM, 94boosted said:

I had the entire exhaust system replaced under warranty on my 2015 5.3 at 27K miles, 14 months later and now at 38K miles the noise is back. Take it to my dealership and they refuse to replace it, worst part is my comprehensive warranty expired 3 days ago. Such an awful dealership. What are my options? Is there any way to force the valve to stay open? Or if I get some sort of a piggy back tuner that disables AFM does the valve permanently stay open?

I believe the valve was redesigned and may not be as easy to keep open as it was with the older exhaust. I ended up with the same problem with the squeak again, and bought a Borla Atak exhuast system. I like how loud it is, but it probably pisses off the neighbours on cold start in the early morning.

94boosted · December 12, 2018

On 12/3/2018 at 9:32 PM, n1ghtsh1ft said:

I believe the valve was redesigned and may not be as easy to keep open as it was with the older exhaust. I ended up with the same problem with the squeak again, and bought a Borla Atak exhuast system. I like how loud it is, but it probably pisses off the neighbours on cold start in the early morning.

Good to know. Do you know if the valves default position is open and it only closes during 4cyl mode?

300 Blackout · December 12, 2018

Good to know. Do you know if the valves default position is open and it only closes during 4cyl mode?

Default closed. Opens with V8

94boosted · December 12, 2018

34 minutes ago, 300 Blackout said:

Default closed. Opens with V8

Good to know, thanks. So how do all those AFM delete controllers/tunes work? Just force the valve to stay open as soon as vehicle is turned on?

300 Blackout · December 12, 2018

Good to know, thanks. So how do all those AFM delete controllers/tunes work? Just force the valve to stay open as soon as vehicle is turned on?

The valve is not controlled by the tune. The valve doesn’t have any electronics, it’s simply a butterfly valve with constant spring pressure that defaults to the closed position until enough exhaust pressure causes the valve to open completely.

The truck always starts in V8 so the AFM delete really isn’t doing anything different than normal at startup. It simply doesn’t allow the truck to exit V8, therefore, the valve always stays open (until you shut off the truck).

Easiest way to disable the valve is with a clamp. Get a wrench, manually turn the valve to the open position and clamp it there. If you leave AFM active with the valve clamped open, you’ll likely hear what is described as the “chopper” noise when traveling in V4 mode. It’s entertaining to say the least. You’ll feel like George Jetzin puttering down the highway.

The other option is to cut the valve out. Most guys who do this cut out their muffler and straight pipe from the 3rd cat to just behind where the valve used to be. If you leave the resonator (looks like a smaller muffler above the rear axle), you actually end up with a nice sounding exhaust. Cost is about $50 at a muffler shop. Takes less than 30 minutes.