AFM Didn't Turn on This Morning!?

SkiDooNick700 · November 13, 2019

Update: Conclusion - it was just friggin cold! And I wasn't driving hard at all, probably never was able to really heat things up with my putzin to work.

Hey all.

Drove into work this morning, about a 13 mile commute. Engine got up to operating temp probably 5 or 6 miles into the commute. Tranny was at 132 degrees when I parked. Air temp of 6F. AFM never once activated the entire drive in. It's usually on a lot especially since most of my commute is between 25 - 45mph. I also notice my engine idle speed never settled down to ~500rpm like it usually does. It wanted to stay a tick under 750rpm, probably was at 650 to 700rpm idle.

Is there some AFM criteria that the computer never met on my commute in this morning due to the cold temps? Is there some other underlying issue? Will be curious to see if it works on my way home today.

I'm not really complaining, it was nice to have all 8 gears this morning and not have the dreaded v4 drone with my Venom 250 exhaust or run in M7 to avoid v4!

Edited November 13, 2019 by SkiDooNick700

Bob2C · November 13, 2019

Mine did it yesterday morning. I usually run an afm disabler but took it off because I was going to have an emissions test later in the day. I think it’s normal just due to the cold weather and probably some emissions. Just a guess here. If your running an aftermarket exhaust you really should get the range device so it will stay in v8 mode and you won’t have to listen to the drone.

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g2full · November 13, 2019

I remember reading somewhere that there were indeed certain conditions that needed met for AFM to enable. I wouldn't worry with it. If a problem is present you'll get the money light.

Also, agree you should look towards a tuner/afm disabler to turn that crap off permanently.

SkiDooNick700 · November 13, 2019

I came really really close to buying the Range AFM disabler when a member here posted an ebay link or something to someone who had them for sale for like $100 bucks or something. Ended up not doing it. I think I would rather get a tune, however, I am not doing that til out of warranty. I've already had over $3,000 worth of warranty work on this engine and I am happy as hell I didn't have a tune. I know people always say "dealer has to prove it", but, I'm not dealing with that. M7 works for now. 6 more months then I am free

g2full · November 13, 2019

9 minutes ago, SkiDooNick700 said:

I came really really close to buying the Range AFM disabler when a member here posted an ebay link or something to someone who had them for sale for like $100 bucks or something. Ended up not doing it. I think I would rather get a tune, however, I am not doing that til out of warranty. I've already had over $3,000 worth of warranty work on this engine and I am happy as hell I didn't have a tune. I know people always say "dealer has to prove it", but, I'm not dealing with that. M7 works for now. 6 more months then I am free

Makes sense to me. I'm for-fitting about 20k miles of powertrain, but am justifying that with my A/M extended warranty... and the fact that when the truck just went in for pushrod and lifter issues I wasn't aware that I had any powertrain left to begin with.

6 months isn't that long. I went with BlackBear myself. Still in the waiting process. I sent off my data logs and factory tune files last Friday and was added to the to-do list.

Also, another thought to add to my earlier response... I remember seeing someone post about the conditions of AFM on here but more so how GM is so secret about what conditions cause it to come on. Most of what has been figured out about when the AFM comes on has been from owner's playing around and just watching it. I do specifically remember reading somewhere though that if all systems aren't up to operating temp it won't kick on. I know on my wifes previous vehicle (honda) if the vehicle wasn't up to operating temp their version of AFM wouldn't come on at all.

SkiDooNick700 · November 13, 2019

6 minutes ago, g2full said:

Makes sense to me. I'm for-fitting about 20k miles of powertrain, but am justifying that with my A/M extended warranty... and the fact that when the truck just went in for pushrod and lifter issues I wasn't aware that I had any powertrain left to begin with.

6 months isn't that long. I went with BlackBear myself. Still in the waiting process. I sent off my data logs and factory tune files last Friday and was added to the to-do list.

Also, another thought to add to my earlier response... I remember seeing someone post about the conditions of AFM on here but more so how GM is so secret about what conditions cause it to come on. Most of what has been figured out about when the AFM comes on has been from owner's playing around and just watching it. I do specifically remember reading somewhere though that if all systems aren't up to operating temp it won't kick on. I know on my wifes previous vehicle (honda) if the vehicle wasn't up to operating temp their version of AFM wouldn't come on at all.

I'll definitely go with BlackBear, they did my last truck. But I am also thinking to just save the money as I have some interest in this new Duramax. I have a lot of time to think on this though. I also remember this same post you are mentioning. I think it was from @newdude a few years back, but I could be wrong!

aseibel · November 13, 2019

1 hour ago, SkiDooNick700 said:

Is there some AFM criteria that the computer never met on my commute in this morning due to the cold temps? Is there some other underlying issue? Will be curious to see if it works on my way home today.

Cylinder deactivation may be inhibited for many reasons including the following:

•   Engine coolant temperature out of range for cylinder activation
•   Engine vacuum out of range
•   Brake booster vacuum out of range
•   Transmission gear incorrect or shift in progress
•   Accelerator pedal out of range or rate of pedal application to fast
•   Engine oil pressure and temperature out of range
•   Engine speed out of range
•   Vehicle speed out of range
•   Minimum time in V8 mode not met
•   Maximum V4 mode time exceeded
•   Decel fuel cutoff active
•   Reduced engine power active
•   Torque management active
•   Catalytic converter over temperature protection active
•   Piston protection active, knock detected
•   Cylinder deactivation solenoid driver circuit faults

borrowed from this post:

g2full · November 13, 2019

6 minutes ago, aseibel said:

Cylinder deactivation may be inhibited for many reasons including the following:

•   Engine coolant temperature out of range for cylinder activation
•   Engine vacuum out of range
•   Brake booster vacuum out of range
•   Transmission gear incorrect or shift in progress
•   Accelerator pedal out of range or rate of pedal application to fast
•   Engine oil pressure and temperature out of range
•   Engine speed out of range
•   Vehicle speed out of range
•   Minimum time in V8 mode not met
•   Maximum V4 mode time exceeded
•   Decel fuel cutoff active
•   Reduced engine power active
•   Torque management active
•   Catalytic converter over temperature protection active
•   Piston protection active, knock detected
•   Cylinder deactivation solenoid driver circuit faults

Thank you! I knew there was a list somewhere...

SkiDooNick700 · November 13, 2019

Thanks for sharing that list @aseibel . Man ,I hope it isn't a vacuum issue lol! I'm simply guessing which I think doesn't apply to me. I will follow up on this after I drive home.

~~•   Engine coolant temperature out of range for cylinder activation~~
•   Engine vacuum out of range
•   Brake booster vacuum out of range
•   Transmission gear incorrect or shift in progress
•   Accelerator pedal out of range or rate of pedal application to fast
•   Engine oil pressure and temperature out of range
•   Engine speed out of range
•   Vehicle speed out of range
•   Minimum time in V8 mode not met
•   Maximum V4 mode time exceeded
•   Decel fuel cutoff active
•   Reduced engine power active
•   Torque management active
•   Catalytic converter over temperature protection active
•   Piston protection active, knock detected
•   Cylinder deactivation solenoid driver circuit faults

aseibel · November 13, 2019

I'd still guess it had to do with the temperature. You said it was 6 degrees. Likely it never triggered the system that it was in the "ok to operate" range. If you had the Heater on full blast and defrosters and heated seats, it may have just been struggling to manage all the electrical systems while cold.

Grumpy Bear · November 13, 2019

1 hour ago, SkiDooNick700 said:

Thanks for sharing that list @aseibel . Man ,I hope it isn't a vacuum issue lol! I'm simply guessing which I think doesn't apply to me. I will follow up on this after I drive home.

~~•   Engine coolant temperature out of range for cylinder activation~~
•   Engine vacuum out of range
•   Brake booster vacuum out of range
•   Transmission gear incorrect or shift in progress
•   Accelerator pedal out of range or rate of pedal application to fast
•   Engine oil pressure and temperature out of range
•   Engine speed out of range
•   Vehicle speed out of range
•   Minimum time in V8 mode not met
•   Maximum V4 mode time exceeded
•   Decel fuel cutoff active
•   Reduced engine power active
•   Torque management active
•   Catalytic converter over temperature protection active
•   Piston protection active, knock detected
•   Cylinder deactivation solenoid driver circuit faults

AFM is a load based system. When it gets cold like this it takes more pedal to run the same speed. I has a threshold. Even a fraction of a percent will hold it out. You can check this for yourself with a coast down test. The distance it takes to coast in gear from one speed to another. I have a spot where I do this from 45 mph to 30 mph. In the summer that distance is about 40% further than mid winter. Just wheel bearing grease can have this effect even if everything else is on the money. That said you noted that the idle speed never came down meaning the some temperature requirement wasn't being met. IAT perhaps? Trans fluid temp more likely. 104 F will get you normal transmission function but not full warm ECU functions (idle speed is part of engine speed). Lastly it takes much longer to bring your fluids to full heat in the winter time. Your heating your oil on the first start of the day from perhaps a few degrees below the current air temperature. Think heating your oil from 0 F vs 90 F. Same reason it take longer to microwave something from the refrigerator than from room temperature. AFM is held out until all parameters are met. I wouldn't give it a second thought. Relax and enjoy the day.

It's Tim · November 13, 2019

12 minutes ago, Grumpy Bear said:

Relax and enjoy the day.

+1, already too many distracted drivers...

https://www.cdc.gov/motorvehiclesafety/distracted_driving/index.html

SkiDooNick700 · November 13, 2019

55 minutes ago, Grumpy Bear said:

AFM is a load based system. When it gets cold like this it takes more pedal to run the same speed. I has a threshold. Even a fraction of a percent will hold it out. You can check this for yourself with a coast down test. The distance it takes to coast in gear from one speed to another. I have a spot where I do this from 45 mph to 30 mph. In the summer that distance is about 40% further than mid winter. Just wheel bearing grease can have this effect even if everything else is on the money. That said you noted that the idle speed never came down meaning the some temperature requirement wasn't being met. IAT perhaps? Trans fluid temp more likely. 104 F will get you normal transmission function but not full warm ECU functions (idle speed is part of engine speed). Lastly it takes much longer to bring your fluids to full heat in the winter time. Your heating your oil on the first start of the day from perhaps a few degrees below the current air temperature. Think heating your oil from 0 F vs 90 F. Same reason it take longer to microwave something from the refrigerator than from room temperature. AFM is held out until all parameters are met. I wouldn't give it a second thought. Relax and enjoy the day.

Valid points. I'm not trying to make mountains out of mole hills. I am just curious about this

Grumpy Bear · November 13, 2019

5 hours ago, SkiDooNick700 said:

Valid points. I'm not trying to make mountains out of mole hills. I am just curious about this

Didn't think you were. Curiosity and learning winds my watch.

SkiDooNick700 · November 13, 2019

Alright everyone, 22F on the way home. AFM was kicking on within about 2 miles. So yea that colder temp of 6F must have made the difference.

Maybe I drove too relaxed this morning @Grumpy Bear and she wasnt able to build up enough heat to actually get "hot" so to speak , haha. Next time Ill have to give er a little more to see if i can get AFM to work in the single digit.