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SOLVED! 2012 Yukon XL electronics haywire, power lag while accelerating


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Randomly while driving, the dash lights will go nuts and all the door locks will flicker really quickly. When this happens, the battery gauge dips down below 14. This is accompanied by a loss of power. The whole thing lasts for a couple seconds. 

 

Also randomly while driving, the engine will idle roughly...kind of feels lumpy for lack of a better term...like it’s a running clothes dryer with a shoe in it. When this happens, it seems to have a major power lag accelerating from a dead stop. 

I get no CEL from either occurrence. 

 

We’ve had it for 8 months. It has 132k miles on it. I’ve searched and so far, I have an idea to replace the ground cable for the battery. 
 

Any other ideas?

Edited by Chebby
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Check/clean grounds, check/replace battery cables (both, not just the negative cable).  Also, have battery tested...if it's the original battery, it's been on it's last leg for a couple of years now.  The GMT900 trucks/SUVs do not like it when the battery starts going bad; all kind of electrical gremlins occur when the battery starts dying.

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1 hour ago, dsr611 said:

Check/clean grounds, check/replace battery cables (both, not just the negative cable).  Also, have battery tested...if it's the original battery, it's been on it's last leg for a couple of years now.  The GMT900 trucks/SUVs do not like it when the battery starts going bad; all kind of electrical gremlins occur when the battery starts dying.

Thanks for the reply. I put a new battery in it when I got it. Autozone Duralast Gold. It died 6 weeks later. Autozone swapped it out for me, and I’ve been on the replacement battery ever since. Surely I don’t have two problematic batteries in a row?

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Going to clean and check terminals yet again. This battery is just over 6mo old. The last one that failed was less than a couple months old.

 

This is frustrating.

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Well I checked the terminals. Everything was snug, and they didn’t look dirty at all, but I got my terminal brush out and cleaned them again really well. Hooked everything back up, and drove it around a bit.

 

The battery is now showing just over 14V instead of just under. And no acceleration lag. 
 

I do still have the slightly lumpy idle though. 
 

Maybe it’s time to check spark plugs. It’s VERY irregular, though. Doesn’t feel like I’m missing spark in a cylinder. 

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Well, the Yukon finally threw a code. P0307, misfire in cylinder 7. 
 

I bought new plugs and wires and some AC Delco upper engine cleaner. Shot each cylinder full of that stuff and took my youngest to his soccer game. Came back and finished swapping plugs. No more rough idle, no power lag. That cylinder 7 plug was fouled beyond belief. 
 

Bought a Range AFM disabler. Hoping our plugs last longer and we don’t consume as much oil. 

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8 hours ago, Colossus said:

Yikes, how did the other plugs look? 

Here they all are. The red pliers are the front of the engine. #7 looked far worse than all the others. 

36471567-9382-4BD6-BDB0-718CE3BBE430.jpeg

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On 9/16/2020 at 8:51 PM, Chebby said:

Well I checked the terminals. Everything was snug, and they didn’t look dirty at all, but I got my terminal brush out and cleaned them again really well. Hooked everything back up, and drove it around a bit.

 

The battery is now showing just over 14V instead of just under. And no acceleration lag. 
 

I do still have the slightly lumpy idle though. 
 

Maybe it’s time to check spark plugs. It’s VERY irregular, though. Doesn’t feel like I’m missing spark in a cylinder. 

The charging system is a kind of smart charger, the voltages will vary based on certain parameters, look up the terms RVC, Regulated Voltage Control and EPM, Electrical Power Management.  As for #7, you could very well have a de-ac lifter on its way out.  Dirty oil is AFMs worst enemy, in addition the VLOMs solenoids get out of time as they wear which causes the lifters to collapse.  Multiple short drives do not allow the battery to become fully charged.    

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  • 1 year later...

Checking back in on this thread. The Yukon XL is at 155k miles now, and I have been using a Range AFM Disabler. I haven’t fouled up any cylinders like before, although #7’s spark plug again looks a bit older/dirtier than the others, even though they were all replaced. The electrical haywire issue still happens randomly, but if I remove the battery cables and clean the terminals (which do not in any way appear to be dirty or loose), it goes away for a few thousand miles. Just weird.

 

The thing I like about this Yukon XL is that it has the heavy duty towing package, rated for 8k lbs. That comes in handy. But I’m also getting sick of dealing with issues. It blew a heater core hose last year and stranded my wife on the highway. Second time it has stranded her on the side of the road.

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2 hours ago, Chebby said:

Checking back in on this thread. The Yukon XL is at 155k miles now, and I have been using a Range AFM Disabler. I haven’t fouled up any cylinders like before, although #7’s spark plug again looks a bit older/dirtier than the others, even though they were all replaced. The electrical haywire issue still happens randomly, but if I remove the battery cables and clean the terminals (which do not in any way appear to be dirty or loose), it goes away for a few thousand miles. Just weird.

 

The thing I like about this Yukon XL is that it has the heavy duty towing package, rated for 8k lbs. That comes in handy. But I’m also getting sick of dealing with issues. It blew a heater core hose last year and stranded my wife on the highway. Second time it has stranded her on the side of the road.

How old is the battery?  More than 4 years?  Do you have an advanced, bi-directional scan tool?

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17 hours ago, swathdiver said:

How old is the battery?  More than 4 years?  Do you have an advanced, bi-directional scan tool?

It’s not the battery. It has done this with 3 batteries over the past few years. Current battery is not yet two years old.

 

I just have an OBD reader.

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On 8/29/2022 at 5:42 PM, Chebby said:

It’s not the battery. It has done this with 3 batteries over the past few years. Current battery is not yet two years old.

 

I just have an OBD reader.

 

Well, when you are ready to get serious and solve these issues, get a Tech-2 so you can work on this thing.  Use it along with the troubleshooting guide from the shop manual, like AllDataDIY to find out what is causing the electrical gremlins, might be time for a new BCM.  You can also use to test out the AFM system, probably need a new lifter or two on number 7 or possibly pushrods or valve springs.  

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