Flashing engine light then no AFM cylinder deactivation

59yukon01 · Nov 12, 2024

On the way home tonight doing highway speeds my 2016 GMC Yukon SLT engine light flashed about a dozen times and then went off. Truck showed no signs of misfiring and ran completely normal.

However I noticed it no longer switched down to 4 cylinder at slower speeds like normal. Truck only has 91,000 miles and has been trouble free so far.

Any advice/help appreciated.

ReaperHWK · Nov 13, 2024

ummmmmm. Scan it?

I also wouldn’t drive it until you get the codes. Flashing means misfires and if serious and/or multiple can damage the engine.

59yukon01 · Nov 13, 2024

ReaperHWK said:
ummmmmm. Scan it?

I also wouldn’t drive it until you get the codes. Flashing means misfires and if serious and/or multiple can damage the engine.

That's my plan, but unfortunately have to drive it to my mechanic friend this morning to do I do.

Marky Dissod · Nov 13, 2024

Your Engine Half@$$ disabled itself? AWESOME.
Actually, you need to find out WHY it disabled itself.

Any other symptoms at all whatsoever?

fondupot · Nov 13, 2024

I am pretty sure AFM will disable when an engine light is presented.

Marky Dissod · Nov 13, 2024

fondupot said:
I am pretty sure AFM will disable when an engine light is presented.

Depends on which trouble code(s) is/are being set.

59yukon01 · Nov 13, 2024

Drove it today and everything was normal including cylinder deactivation. Ran great as always. Had it scanned by a friend and no stored codes. Another friend I was hoping to get to today said he's more interested in seeing the data but he suspects a lifter stuck in its guide ......maybe temporarily. He's an extremely knowledgeable mechanic that owns his automotive shop.

Definitely don't want to pretend it didn't happen but it's making me want to consider the Range Technology Disabler going forward.

ReaperHWK · Nov 13, 2024

59yukon01 said:
Drove it today and everything was normal including cylinder deactivation. Ran great as always. Had it scanned by a friend and no stored codes. Another friend I was hoping to get to today said he's more interested in seeing the data but he suspects a lifter stuck in its guide ......maybe temporarily. He's an extremely knowledgeable mechanic that owns his automotive shop.

Definitely don't want to pretend it didn't happen but it's making me want to consider the Range Technology Disabler going forward.

You changing with synthetic oil every 5k?? Clean oil is paramount to keep these engines running well with AFM. I have 160k miles on my 2015 and no issues with AFM.

59yukon01 · Nov 13, 2024

ReaperHWK said:
You changing with synthetic oil every 5k?? Clean oil is paramount to keep these engines running well with AFM. I have 160k miles on my 2015 and no issues with AFM.

Yes oil changed on schedule at my local GMC dealer. Also will be taking it in soon for the recommended 90K mile service.

B-train · Nov 14, 2024

59yukon01 said:
Drove it today and everything was normal including cylinder deactivation. Ran great as always. Had it scanned by a friend and no stored codes. Another friend I was hoping to get to today said he's more interested in seeing the data but he suspects a lifter stuck in its guide ......maybe temporarily. He's an extremely knowledgeable mechanic that owns his automotive shop.

Definitely don't want to pretend it didn't happen but it's making me want to consider the Range Technology Disabler going forward.

If you want a RANGE device, I have one I don't use. PM me if interested.

Flashing engine light then no AFM cylinder deactivation

59yukon01

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