2003 yukon 6.0 engine light on-code-P0174

[weehunt]

Engine light came on about two months ago and I can`t figure out what the problem is. The manuel said if you change brands of gas this might cause it but since I have ran two tanks of 93 oct. through it with no help. I put new plugs in it-no help. I took it to auto zone and they hooked it up and said the MAF was bad. I bought a new one and the light went off for about three days and came back on.Took it back to auto zone and the puter said code P0174-(the pcm has determined that during testing, the fuel system for bank 2 was too lean. Bank 1 identifies the location of cylinder #1, while bank 2 identifies the cylinders on the opposite bank) They couldn`t tell me what was wrong, Just referred me to a mechanic. I like fixing things myself if at all possible. If anyone can help, I would greatly appretiate it. This is a 2003 Yukon Denali xl with 80000 miles on it. 6.0 motor Thanks again for any help!!

[maxwedge]

Any air entering the engine unmetered can cause this, vacuum leak for sure, low fuel pressure, any misfire ( you'd know this). Try cleaning the maf, careful and use specific maf cleaner such as CRC. On rare occassions the o'2 can cause this also.

[weehunt]

I`ve already replaced the MAF and the light went off for a few days and ran fine then it came back on and started idling and running a little rough. Last night I checked all the couplings between the air box and the intake and found nothing. I also took all four(I think that`s all of them) O2 sensors out and brushed them off with a wire brush. The wife said it was running smoother this am but the light is still on. Thanks for your input again!
The wife just came home and said it was running rough again. Clueless in Ky.!!!!!!!!

[GMMerlin]

The PCM controls the air/fuel metering system providing the best possible combination of driveability, fuel economy, and emission control. Fuel delivery is controlled differently during Open and Closed Loop. During Open Loop, the PCM determines fuel delivery based on sensor signals without oxygen sensor ) input. During Closed Loop, the O2S inputs are added and used by the PCM to calculate short and long term fuel trim fuel delivery adjustments. If the O2S indicate a lean condition, fuel trim values will be above 0 percent. Short term fuel trim values change rapidly in response to the heated oxygen sensor voltage signals. Long term fuel trim makes coarse adjustments in order to maintain an air/fuel ratio of 14.7:1. If the PCM detects an excessively lean condition, DTC P0174 sets.
Check for leaking intake manifold seals around the intake ports. The intake gasket seals may be leaking around the intake ports, causing a lean condition. Many times they will leak around the bottom side of the port
The intake plenum should also be checked for excessive warpageVisually and physically inspect the following items:
The vacuum hoses for splits, kinks, and proper connections.
Fuel contamination

[weehunt]

The light went off the next day after I cleaned the o2 sensors. Ya think maybe that was the problem? Thanks