17 tahoe Afm Disabler /conflicts/Issues?

[1Tahoe7]

I just joined this forum and I’m new to posting, but I wanted to ask for some advice. I recently bought a 2017 Tahoe LT with the 5.3. It has about 180k miles on it. I was aware of the AFM issues when I bought it and knew what I was getting into. One of the things that helped sell me on it was that it had a brand-new transmission installed less than 20k miles ago and I have the paperwork for it.


After buying it, the AFM never seemed to work quite right. It felt like it had trouble going into 4-cylinder mode and would only work intermittently. After the first couple of days of owning it, I bought an AFM disabler from Boost. Once I installed it, all of those issues went away and the engine runs much smoother.


One thing I have noticed, though, is that if I let it idle when the engine is up to temperature—like sitting in a parking lot waiting on my kids—the temperature gauge starts to rise slightly above the center mark. Once I start driving again, it goes back down to normal.


I was wondering if the AFM disabler could somehow affect the fan operation or fan switch. I checked under the hood and the cooling fans are running, but they seem to be at a fairly low speed.


Has anyone experienced something similar? Don’t the cooling fans automatically adjust speed based on engine temperature?

 

[Fless]

Statements and questions might be easier to understand it they were broken up into more than two sentences.

 

[1Tahoe7]

Statements and questions might be easier to understand it they were broken up into more than two sentences.

My bad!!

 

[Marky Dissod]

... if I let it idle when the engine is up to temperature - like sitting in a parking lot waiting on my kids - temp gauge starts to rise slightly above the center mark.
Once I start driving again, it goes back down to normal.

GM OE fan settings let the coolant temps approach disturbingly close to overheating, in the name of a slightly better MpG score.
Best chance to notice this is when idling, especially in a tailwind that'd work against the radiator fans, and especially if it's REALLY hot out.

I was wondering if the AFM disabler could somehow affect the fan operation or fan switch.

AFM / Engine Half@$$ is disabled under a certain coolant temp in the GM OE tune to protect the engine.
(Chrysler's early V4 mode was allowed even when the engine was cold enough to cleave the block in twain.
Although I very strongly doubt that there's an AFM disabler that tricks the engine to avoid V4 mode by tricking the ecm into thinking the coolant is colder than actual,
because that would demand an excessively rich mixture that would cost so too much MpG and accelerate wear.
There are other parameters that can prevent V4 mode, but the only one that I can think of that would also affect fan operation would be to lie about coolant temp,
and that's a bad idea for a whole lot of good reasons.

Someone ought to try driving around while gathering real time data, both with AFM disabler installed, and without, and compare,
so that a definitive answer to your question can be found. Same goes for figuring out how the DFM disabler works too:
They both tell the ecm at least one lie, of commission, or omission, to prevent Engine Half@$$ / Cylinder Confusion from taking effect.

I checked under the hood and the cooling fans are running, but they seem to be at a fairly low speed.
Has anyone experienced something similar? Don’t the cooling fans automatically adjust speed based on engine temperature?

In the early 90s GM fans work like this: one fan on = Low, two fans on = High
By the late 90s GM fans work like this: both fans on in series = Low, both fans on in parallel = High
By the mid noughts GM fans went from distinct Low & High speed settings, to a far more gradually progressive PWM function;
as coolant temp goes a lil bit, both fans' blow a lil bit, as coolant temp goes up a lil more, both fans blow a lil more, and so on.
However GM OE fan programming only allows 'MAX' fans' speed at around 108C / 228F if I remember correctly.
GM has been doing this in the name of improving MpGs and emissions, at the cost of durability & longevity.
Cure for this is - as it has been since the late 80s on Buick's turbocharged 3.8L - is to have the ecm tuned to suit your tastes.

 

[bigredreality]

What AFM disabler did you purchase? I want to buy a good one.

 

[Marky Dissod]

Which AFM disabler did you purchase?

There are good ones - Range is a name I keep noticing on forums and in vehicles I've been in.
Personally I'd either drive in M5 (6L80E) or M7 (8L90E) til I was SURE I'd found one equal to or superior to the Range, were I interested in one.
Turns out I'm not. An ecm&tcm tune is a FAR better bang for the buck in terms of improved performance, MpG, reliability, durability, and longevity.

 

[bigredreality]

Okay thanks. I will try to find a local tuner to disable the AFM. Maybe that will also help the shifting on the transmission.

 

[Marky Dissod]

I will try to find a local tuner to disable the AFM. Maybe that will also help the shifting on the transmission.

If the tuner you find is competent and thorough, it will DEFINITELY help transmission response, not just durability and longevity.
You'll find other benefits as well. No one ever regrets a good tune - they usually regret not having done it sooner.