V4 mode not working

[divicevich]

Got 3200k miles on my 5.3 LTZ 4x4 and I noticed my gas mileage was not as good as it was a few weeks ago. I do a lot of hwy driving for work so I pay attention to mileage, V4 used to kick in on flat hwy around 70mph now its below 60mph. Even driving at slow speeds through the neighborhood it stays in V8. Anyone else experience this issue, if so what was the correction. Going to dealer next week.

[Daryl LBZ]

A good correction would be to leave it that way.

[svtkidd23]

Leave it!

[mzodarg]

Hopefully soon mine won't work either. By choice of course.

 

Mike

[MikeNH]

You driving in M4 or M5? On the 900-series trucks that'll disable AFM.

[Silver space ship]

Mine hasn't been coming on much at all lately but I put heavier tires on and it's been cold out. It's only coming on going down hill and speeds around 45 mpg or lower. Even before the new tires I started noticing it not coming on when it seemed like it should before. For thanks giving I drove about 300 miles on some of the flattest roads in the state and drove 60 with the cruise on and with the stock tires and it wouldn't go into v4 until I would slow down for towns. No wind either but it was -1F out, I only got 18.5 for an average. same trip in the summer it would have been in v4 most the way and I bet I would have got 21 to 22. I think the cold and winter fuel reduces how much it will go in v4.

[Cap'n Pete]

Fuel economy always drops substantially in the cold weather. You would "think" that the cold charge of air would help boost power and maybe improve mileage, but it's probably due to the cold, dense air, requiring more fuel to keep the A/F ratio in spec?? And the winter fuel must not give the same bang for the buck?!?!

[TJay74]

Yeah my 2014 6.2 is not going in it much at all either. I almost never goes into V4 on the highway at all and rarely does it while driving around town.

[anthony2558]

Yeah it probably has a lot to do with the colder air and winter gas. I've noticed mine not doing the V4 as much in the morning when its a lot colder out. Weeks ago it would go into V4 more often, but it was warmer then.

 

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[divicevich]

Did go up 1" larger on the tire size but wouldn't think it would affect it. My brother in law has the same truck just 2 wheel drive and on the hwy yesterday in his truck he had the cruise set at 71 and was in V4 mode. I guess its not that big of a deal but just trying to get the best gas mileage possible. I have switched to the premium Shell fuel on my last two tanks to see if it made a difference in performance, would the higher octane level have any affect on the AFM?

[ace ventura]

Your probably going to have to get a Programmer to adjust for the change in tire size. That will assist in it going into v4 mode as well.

[anthony2558]

It may have a effect on AFM only because the computer may be relearning and readjusting to the higher octane. Two tank fulls, i would assume that its learned and made its adjustments by now tho.

 

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[mzodarg]

Yeah it probably has a lot to do with the colder air and winter gas. I've noticed mine not doing the V4 as much in the morning when its a lot colder out. Weeks ago it would go into V4 more often, but it was warmer then.

 

Sent from my XT1053 using Tapatalk

Last three days in Oklahoma it's been in the teens. My V4 mode activates like it did when it was 70 outside.

 

Mike

[DanielAcosta]

Programming my speedometer for oversize tires definitely helped increase operation in V4. I actually made a mistake and had too large a tire size plugged in and it stayed in V4 mode even more. I quickly discovered my mistake and corrected it; right now my speedometer/odometer error is 0.2% (0.2 miles per 100 miles).

 

So what I learned is with oversize tires your speedometer reads lower than your true speed, so the truck stays in V8 because it thinks you need the power to get up to the speed you should be at for your given throttle opening. Originally my speedometer/odometer error was 8% because of my tires, so I'm happy with the correction to virtually zero error. No, the mileage didn't go up by 8% (probably closer to just 3-4%), but every little bit helps. Plus it makes it a little less likely to get a speeding ticket with an accurate speedometer.

 

See my signature block and photo gallery http://www.gm-trucks.com/forums/gallery/album/2371-gas-mileage/ for more info on my mods and mileage. One of my galleries has DIC mileage displays in response to those who didn't believe I was really getting 20-22 mpg with 34" tires.

[divicevich]

Checked into the hypertech calibration and was wondering since I only increased tire diameter by 1" would it make a difference. Speedometer is only off by 1 or 2mph. I know if I call hypertech they would probably say yes but before I invest 200 franklins I want to know if this is really gonna make a difference.