Help!! DTC P1174...

[mt8881]

P1174...its been intermittent until a few days ago. Engine light would come on in the morning and go off at night. Currently its on all the time. New HO2 sensors, new knock sensor, cleaned throttle body and MAF sensor. Drivability isnt affected, the only thing i notice is MPG is down a little. This afternoon i checked injectors and resistance on all 8 are between 13.5 and 13.8 ohms. Anyone else have this issue? Any ideas?


2008 Tahoe LT
5.3 Flex Fuel
74k miles

 

[rockenthebowtie]

Possible upper intake manifold gasket vacuum leak, get some carb spray and spray around the upper intake gasket and listen for a change in the rpm

 

[mt8881]

I will have to give that a shot. I even got a new gas cap for it. The old cap was a bit loose. Im totally stumped on this..and theres almost no information out there on it. Im also gonna pull the plugs out since they are pretty easy to get to.

 

[rockenthebowtie]

That DTC is bank 2 fuel trim lean meaning that there is un-monitored air going into combustion chamber on the passenger side of engine and most likely its going to be around that intake gasket area

 

[mt8881]

Are you sure its bank 2? Every scanner ive hooked it up to says its fuel trim balance bank 1...

 

[mt8881]

And nothing is said about it being rich or lean...

 

[MO Viet Vet]

Bank 1 or bank 2 doesn't matter. If in fact it is the intake gasket leak you will fix all at the same time anyways. Read this:

DTC P1174
Fuel Trim Cylinder Balance
CIRCUIT/SYSTEM DESCRIPTION
The Fuel Trim Cylinder Balance diagnostic detects a rich or a lean cylinder-to-cylinder air/fuel ratio imbalance. The diagnostic monitors the pre-catalyst heated oxygen sensor (HO2S) signal's frequency and amplitude characteristics by calculating an accumulated voltage over a predetermined sample period. An imbalance is indicated when multiple samples of the accumulated voltage are consistently higher than the desired value.


The common denominator is that you have replaced all related items and the only thing left is the mechanical condition of the engine, the intake gasket leak. Engine is known for this because the oe gasket sealing ridges get distorted from poor design. The Felpro gasket kit is the way to go as well as AC Delco Knock sensors while in there and the harnesses from either AC Delco or Dorman. Look at you tube for the step by step.

By the way, I would not argue with ElGuapo, rocken, this early in the morning. He's not himself when he is cranky. Give him a Snickers.

 

[rockenthebowtie]

Yes i stand erected, i mean Corrected lol it is bank 1 drivers side of engine check for vacuum leaks poor connectins at injectors, pcv hose for cracks possibly even a bad fuel injector, thanks for catching that

 

[mt8881]

Just a little update...new plugs..and no vacuum leaks..same code. The live data on my code scanner is showing negative fuel trims on both sides. Could i possibly have a bad MAF sensor?