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

[basstracker89]

 

[testdepth]

Truck sat overnight and I just got back from driving it. No problems this morning as in the video. Drove normally. Like I said it's random. I was hoping it would completely fail but no such luck.



I bought a fuel pressure gauge and transmission test gauge. As soon as it cools off I'll get to testing.

 

[testdepth]

Fuel pressure gauge connected to fuel rail test port reads:
Key on 55psi
Engine start initially at 60psi
Engine start at idle 600 rpm 43 psi and stays there
I watched the gauge and it never moved from 43psi no matter what rpm I went up to

With my scanner connected
Desired fuel pressure in park idling at 600rpm shows 43psi
Fuel pressure sensor shows 43psi
Holding gas pedal at 1000rpm, 2000rpm and 3000rpm : fuel pressure stays constant 43psi and never changes.

 

[testdepth]

I'm being told 43psi is normal.

 

[sniper22]

Fuel pressure gauge connected to fuel rail test port reads:
Key on 55psi
Engine start initially at 60psi
Engine start at idle 600 rpm 43 psi and stays there
I watched the gauge and it never moved from 43psi no matter what rpm I went up to

With my scanner connected
Desired fuel pressure in park idling at 600rpm shows 43psi
Fuel pressure sensor shows 43psi
Holding gas pedal at 1000rpm, 2000rpm and 3000rpm : fuel pressure stays constant 43psi and never changes.

The pressure shouldn't change if the pump is good. Mechanical pumps would.

I'm being told 43psi is normal.

The fact that it holds the same pressure means its a good pump. 43 psi is okay if its a flex fuel system. Will your scanner run an injector balance test?

 

[testdepth]

The pressure shouldn't change if the pump is good. Mechanical pumps would.

The fact that it holds the same pressure means its a good pump. 43 psi is okay if its a flex fuel system. Will your scanner run an injector balance test?

It is a flex fuel system.

Yes my scanner will run an injector balance test

 

[sniper22]

It is a flex fuel system.

Yes my scanner will run an injector balance test

I would do that and note the fuel pressure. If you can watch live data, I would have someone drive you around watching the temp sensor and mass air flow. Injector and coil grounds can cause tons of ghost issues. Sorry if those have already been covered .

 

[testdepth]

Drove it this morning without any problems. Problem occurs when the truck has cooled off for several hours or sits over night but does so randomly. I'm told 43psi with a flex fuel truck is normal and the fact that it maintains 43psi at all speeds means it's working as it should.

Still don't know what the cause is though.

 

[testdepth]

2007- 2104 GM with 6.2L and 6L80E trans:
Looking for anyone else out there using this engine and transmission having similar problems. 170000 miles on mine. I have searched the internet and cannot find anything. This problem throws no codes or check engine and is random. For instance mine went 9 days without a problem and then one morning it surged and stalled. The next day it surged but didn't stall and the last two days nothing as it drove fine. Does not happen after the engine is at normal temp of 210F. I can't be the only lucky person.

 

[testdepth]

I just pressure tested my 6L80E with a mechanical gauge screwed to the line pressure test port on the passenger side next to the bell housing. (7/16 bolt). Engine at normal temp of 210F.


IDLE WOT

P 84 90

R 80 230

N 85 90

D 65 170

M 65 265

M2 65 160

M3 65 150

M4 65 150

M5 65 150

M6 65 150

Well it looks like these pressures mean my transmission is good.