I got this from a friend:
I’ve been a GM mechanic for 17 years. I need to get something off my chest because it’s been weighing on me for a long time.
Last Thursday a guy drove into my shop in a 2019 Tahoe.
Nice guy. Maybe early 40s. Wedding ring. Soccer cleats in the back seat.
He told me the engine started ticking that morning on the way to drop his son off at practice.
I already knew what it was before I even lifted the hood. I’ve heard that tick a thousand times.
I could call it from across the lot at this point.
Lifter failure. Cylinder 3. Camshaft wiped.
I’ve been at this since 2008. I’ve worked on everything GM puts out.
Silverados. Sierras. Tahoes. Yukons. Suburbans. Escalades.
And I am telling you, I have never seen a single system kill more engines than Active Fuel Management.
AFM. That’s what GM calls it. Since 2007 they’ve been programming their V8s and V6s to shut down half the cylinders while you cruise. Supposed to save fuel. Maybe a mile or 2 per gallon.
The lifters that run it have a tiny locking pin inside them.
Every time the system cycles, those pins lock and unlock. Hundreds of times per drive. Thousands of times a week.
And when that pin gives out, the lifter collapses. It stops spinning and it chews through the camshaft lobe like a chisel on butter.
I do 2 to 4 of these jobs every single month. Sometimes more. And it’s been that way for years.
I’ve pulled apart engines with 31,000 miles on them. I pulled one apart last summer with 24,000 miles. Practically a new truck. Owner had it less than a year.
I’ve seen guys who changed their oil every 3,000 miles with the best synthetic money can buy. Made no difference.
I’ve seen fleet trucks that were serviced by the book, every interval on time, every fluid clean. Made no difference.
The system doesn’t care how well you maintain your truck. When that lifter decides to let go, it lets go. And there is absolutely nothing you can do about it once it starts.
That’s what frustrates me.
Because these are solid engines. The 5.3. The 6.2. Take the AFM system off of them and they’ll run 300,000 miles without breaking a sweat.
I’ve seen it with my own eyes. The pre-2007 trucks, the ones without AFM, those things are bulletproof. I’ve got customers still daily driving them with 260,000 on the odometer.
But GM bolted this system onto a perfectly good motor to squeeze out a couple miles per gallon to hit government fuel economy numbers. And it is wrecking engines that would have lasted a lifetime.
You want to know the hardest part of my job?
I have to call guys like the Tahoe owner from Thursday and break the news that their engine is torn apart and it’s going to run them $4,000 to $8,000 depending on how far the damage spread.
And every single time, the same reaction.
Then “how is that even possible, I just had the oil changed.”
Then I have to walk them through AFM. Something their dealer never once mentioned. Something the salesman never brought up. Something nobody explained to them when they signed the papers on a $58,000 truck.
Thursday’s guy? He still owed $38,000 on the Tahoe. No warranty left. 71,000 miles.
I quoted him $5,400 for the job.
He just stood there in my shop looking at the floor.
That’s the moment that stays with me. Every single time.
About 3 years ago I started recommending a FullForce™ AFM disabler for every GM truck I work on. Every single one.
I don’t care if it’s in for an oil change or a complete rebuild. I bring it up.
It plugs into the OBD2 port under the dash. Takes 2 seconds. And it tells the computer to keep every cylinder firing all the time.
So no more AFM cycling, and no more hammering the lifters every time you get behind the wheel.
It doesn’t reprogram anything. Doesn’t touch the ECU. You unplug it before a dealer visit and there’s absolutely zero trace it was ever installed.
I’ve had customers come back at 40,000, 60,000, 80,000 miles after I put one in.
Zero issues. The trucks run smoother. The shudder everyone assumes is normal disappears completely. And the lifters aren’t getting beaten to death every single drive.
I can’t take back the damage on the trucks that are already sitting on my lift. But I can keep the next one from ending up there.
I’m not writing this for any company. I’m writing this because I’m tired of making phone calls that wreck people’s week.
I’m tired of watching guys run the numbers in their head while they stare at my shop floor.
I’m tired of knowing that a simple plug-in module would have saved them thousands.
If you drive a GM truck or SUV from 2007 or newer with a V6 or V8, you have AFM.
Your dealer probably never said a word about it. The shudder you feel around 40 or 50 mph is the system cycling. And every time it cycles, it’s grinding down the parts that will eventually fail.
I’m asking you to look into this before you end up in my shop. Because I don’t want to make that phone call to you.
EDIT: I should have included this in the original post but the module I recommend in my shop is called FullForce™. Here’s their site:
