Active Fuel Management

a5brooks352 · May 1, 2014

I 2008 Silverado 5.3L V-8, when going from V-4 to V-8 there is a vibration that you can feel and it also seems to shift way too often. What could be the cause of this and is this a serious issue I should be worried about?

Cowpie · May 2, 2014

No. It is common for others to feel the differences going from 8 to 4 and back to 8. And the subsequent gear hunting because of delays. The AFM thing usually is not bad when the road is fairly flat to low, gradual rolling. But anything other than that, and it is less than desirable. The main reason is that it cannot anticipate grade changes. And for an engine to deal effectively with hills and not choke, is to start feeding a little power just before tackling the hill. Cruise is also terrain challenged. Both in combination can lead to a lot of gear hunting by the transmission. It only knows one thing.. you want to go a certain speed, and it will peg all the power it has to, to maintain the speed.

Now all that being said, many just disable the AFM function and really like the results. You can disable by using one of the ECM tuning products, or a simple plug in the OBD port module, that has only one function, to disable the AFM. Both get the job done. I noticed, just driving my new 2013 home after buying, that I wanted to dump the AFM function. I did it a day or two later, at 240 miles on the odometer. Have never regretted it, and like it much better.

Beer Belly · May 2, 2014

Mine is more noticeable below 40mph. Still trying to get used to the Tranny.....that thing can't get to 6th gear quick enough, and I find myself punching the throttle just to pick up an extra 5-10mph on the interstate.....

2017SierraSLT · May 2, 2014

Just eliminate it via a tune and be done with it. The truck will feel more refined and powerful.

GMCustomerService · May 3, 2014

Hello a5brooks352,

As a customer service representative, I'm not able to provide much in the way of do-it-yourself information, so I'm glad to see forum members are beginning to step in with feedback and may have answered your question. If you have any lingering concerns please contact me via private message.

Regards,

Jennifer T.

GM Customer Care

chupe442 · May 3, 2014

Hello a5brooks352,

As a customer service representative, I'm not able to provide much in the way of do-it-yourself information, so I'm glad to see forum members are beginning to step in with feedback and may have answered your question. If you have any lingering concerns please contact me via private message.

Regards,

Jennifer T.

GM Customer Care

Am I the only one that thinks it odd that a GM customer care rep would condone that people are telling him how to bypass the factory settings??

Z45 · May 3, 2014

Keep in mind the GM and its dealers will always put a positive spin on the AFM system.

TSB 06-06-05-001C

"Some customers may comment in a change in the exhaust note or tone when an Active Fuel Management System equipped engine is in 3 or 4 cylinder mode. Some drivers may also notice a very slight vibration in either the accelerator pedal, floor pan, and/or the steering wheel. This is a normal condition for Active Fuel Management System equipped vehicles and no repairs should be attempted."

Customer Information on Active Fuel Management

When the Active Fuel Management System is enabled, physical changes take place within the engine that allow it to run as a 3 or 4 cylinder motor with accompanying additional fuel savings. The change in exhaust tone is expected as all sound from the exhaust is the result of combustion in the engine. The ability to perceive these changes in sound are kept to very minimal levels as the Active Fuel Management System is only activated during a steady state/near steady state driving or during coast down. In both of these situations, the load on the engine is minimal and general exhaust volume (sound) is low. You may give a copy of this bulletin to your customer

PIP4371A

patriot · May 3, 2014

It's all but unnoticeable on mine.

GMCustomerService · May 3, 2014

Hi chupe442,

I understand where you are coming from. I am only here to offer my services to customers who are experiencing an issue with their vehicle. The forum is here for members to give their advice to fellow forum members who are seeking advice. I understand that when vehicles are out of warranty that customers may turn to alternative resolutions to resolve their vehicle issues. I am neither condoning or condemning the advice that fellow forum members are providing. I was simply informing a5brooks352, that GM Customer Care is here if needed.

Jennifer T.

GM Customer Care

chupe442 · May 3, 2014

Hi chupe442,

I understand where you are coming from. I am only here to offer my services to customers who are experiencing an issue with their vehicle. The forum is here for members to give their advice to fellow forum members who are seeking advice. I understand that when vehicles are out of warranty that customers may turn to alternative resolutions to resolve their vehicle issues. I am neither condoning or condemning the advice that fellow forum members are providing. I was simply informing a5brooks352, that GM Customer Care is here if needed.

Jennifer T.

GM Customer Care

I like and appreciate that you are making yourself available to the forum members here and hope I didnt come off too much like a "tool". It just struck me odd on that one. Thanks for being there.