New problem with this 2012 Yukon XL 1500 Denali 6.2L. I really hate this truck! GREMLIN is back

[Dieseldoesnt47]

you have a ground fault. probably between ecm and pcm. possibly at firewall going to body controller. could be getting a little magnetic interference as well. I love the power Chevy stuffs in stuff and I'll swear by 6.0 4l80e forever but in cutting costs someone at Chevrolet long ago decided the distributer was the only necessary electronic device needed to go 200 mph. somehow no one ever realized going from that to an average of 18-20 controller modules would require better electrical components. the shielding on whichever wire decides to dump its electricity to the closest piece of metal is getting war, then subsequently thinning allowing some wire carrying ultra sensitive voltages to pass through, wire is probably skinned inside the loom from factory its not a common issue but I have seen it, someone is gonna have to take the harness apart and visually inspect it, find the wire that is skinned and repair it. it wont throw codes unless its faulting at the time the scanner is hooked up its also gonna make a power probe near useless. its not at all gonna be fun and is a freak occurrence, replacing the whole harness is costly, and about as big of a pain for whoever is wrenching, best advice is to drive it everywhere, when it starts its scizo pay attention to everything it does and what order the defects occur. write it down as soon as you can, do it everytime. It will paint a much better picture for whoever the lucky soul is that gets to try to find it. its gonna be terrible for whoever does the work so unless your really good friends it will be costly but whoever does the work has to know it could take somewhere between 10 minutes and a month and a half to repair. once its fixed. sell it, trade it in, or start leaving it running in sketchy parts of town with the door open everytime. this issue has caused other issues you just cant see right now. also AFM is the gasoline equivalent to dpf systems. if u don't want to be firing on all 8 at all times get a v6 or hell even a hybrid. ( don't get the 3.0 diesel... just dont lol). best transmission on the planet tho.. if you can get it to stop going for limp mode all the time lol.

 

[Dieseldoesnt47]

praying for you.. but its doing an awful lot of craziness for a cylinder misfire, especially for a system that cuts down to 4 cylinders at highway speed. ecm should have saved that code to register on the scanner if thats the case. i hope its fixed but my instincts are screaming ground fault.

 

[Bypass]

View attachment 9487778

There's a bunch like that at the bottom of Little river canyon in Ft Payne Alabama.

 

[testdepth]

I changed out the plug from cylinder 6 and no more misfires. On this truck there is a braided wire ground going from the driver side firewall to the rear of the engine block. I bought a 24" #4 battery cable and a flange bolt to install a new ground cable from the same drive side firewall stud to the front of the engine block.

The truck sat over night and I got in this morning for a test drive. Drove it for 45 minutes. 25 miles at different speeds between 0 - 65 on a straight road and then in stop and go traffic for another 20 miles. No issues and runs like new. Drove it back home and parked it and then ran a scan of everything just in case. No DTCs, warnings or check engine.

Thanks for all the help but I believe it's all repaired now.

So who wants to trade for an SUV with 4wd or buy it?

 

[basstracker89]

I changed out the plug from cylinder 6 and no more misfires. On this truck there is a braided wire ground going from the driver side firewall to the rear of the engine block. I bought a 24" #4 battery cable and a flange bolt to install a new ground cable from the same drive side firewall stud to the front of the engine block.

The truck sat over night and I got in this morning for a test drive. Drove it for 45 minutes. 25 miles at different speeds between 0 - 65 on a straight road and then in stop and go traffic for another 20 miles. No issues and runs like new. Drove it back home and parked it and then ran a scan of everything just in case. No DTCs, warnings or check engine.

Thanks for all the help but I believe it's all repaired now.

So who wants to trade for an SUV with 4wd or buy it?

So how much time and money did it cost?

 

[testdepth]

So how much time and money did it cost?

Less than a $1000 in parts and 5 days of me working on it

 

[prestige30165]

I changed out the plug from cylinder 6 and no more misfires. On this truck there is a braided wire ground going from the driver side firewall to the rear of the engine block. I bought a 24" #4 battery cable and a flange bolt to install a new ground cable from the same drive side firewall stud to the front of the engine block.

The truck sat over night and I got in this morning for a test drive. Drove it for 45 minutes. 25 miles at different speeds between 0 - 65 on a straight road and then in stop and go traffic for another 20 miles. No issues and runs like new. Drove it back home and parked it and then ran a scan of everything just in case. No DTCs, warnings or check engine.

Thanks for all the help but I believe it's all repaired now.

So who wants to trade for an SUV with 4wd or buy it?

Glad you got it fixed. Hard to believe a cable can deteriorate from the inside due to corrosion and have no evidence
on the outside. Took me 2 months to figure out what it was on mine and about 400,00 (Installed New Battery and Alternator)
Change the oil often to help prevent lifters from failing.

 

[Dieseldoesnt47]

The law of thermodynamics states....... Energy = heat. Outer coating keeps it dry lol oxidation is enemy

 

[testdepth]

Well here we are again. I drove the truck and no issues. My wife then went up the road 2 miles to the Circle K and comes back to tell me the truck did the same thing as before. Jerking, RPMs running up and down and acting like it would die.

I put my scanner on it and NOTHING. No DTCs, warning lights and no check engine. I then drove it the same route she took and then went further up the road. Starts and stops, various speeds and turns but the truck was normal so I came back home. I attached my scanner and the only thing I can find at all is under the fuel system it shows something called "Command Air Fuel Equivalence Ratio" the indicated value is in "red" and it's 1.0 .

 

[BillsCamino]

USPS has your solution......