Check it out guys I believe I have found a sure fire way to find out whether or not your truck is affect by the Hesitation, Stalling and Stumbling issue that is spreading throughout this forum like cancer. I realize you can do it by VIN code, but there are other's who believe they have this problem and are not within the VIN specs so here you go, try it at your own risk, it worked for me now I just need to have the TSB applied to my truck at the dealer this week. First, here is a crash course in EVAP systems for those who are curious, otherwise just scroll down..
(out of Chiltons)
1)The fuel and evaporative emissions control (EVAP) system absorbs fuel vapors from the fuel tank and, during engine operation, releases them into the engine intake system where they mix with the incoming air/fuel mixture. The main components of the evaporative emissions system are the canister (filled with activated charcoal to absorb fuel vapors), the purge valve, the vent valve, the fuel tank pressure sensor, the fuel tank and the vapor and purge lines.
2) After passing through a check valve, fuel tank vapor is carried through the vapor hose to the charcoal canister. The activated charcoal in the canister absorbs and stores the vapors. When a programmed set of conditions are met (engine running, warmed to a pre-set temperature,etc.), the PCM opens the purge valve and the vent valve.
Fuel vapors from the canister are then drawn through the purge hose by intake vacuum into the intake manifold and combustion chamber where they are consumed during normal engine operation.
3) The PCM regulates the rate of vapor flow from the canister to the intake manifold by controlling the duty cycle of the EVAP purge valve control solenoid. During cold running conditions and hot start time delay, the PCM does not energize the solenoid. After the engine has warmed up to the correct operating temperature, the PCM purges the vapors into the intake manifold according to the running conditions of the engine. The PCM will cycle (ON then OFF) the purge valve control solenoid about 5 to 10 times per second. The flow rate will be controlled by the pulse width, or length of time, the solenoid is allowed to be energized.
4) The system performs a self-diagnostic check when the engine is started cold. When the programmed conditions are met, the PCM opens the EVAP canister purge valve, leaving the vent valve closed. The action allows the engine to draw a vacuum on the entire EVAP system. Once the proper vacuum level is reached, the PCM closes the purge valve, sealing the system. The PCM then monitors the fuel tank pressure sensor voltage and sets a diagnostic code if a leak is detected.
5) The fuel tank pressure sensor operation is similiar to the MAP sensor. The PCM supplies a 5-volt reference voltage and ground circuit to the sensor. The sensors returns a signal voltage to the PCM which varies according to the air pressure inside the fuel tank. When the air pressure inside the tank is equal to the outside air pressure (as with the fuel filler cap removed), the sensor output voltage is approximately 1.5 volts. With 14 in-Hg vacuum inside the tank the sensor output voltage is 4.5 volts.
Note: THE EVAPORATIVE CONTROL SYSTEM, LIKE ALL EMISSION CONTROL SYSTEMS, IS PROTECTED BY A FEDERALLY-MANDATED WARRANTY (5 YEARS OR 50,000MILES AT THE TIME THIS MANUAL WAS WRITTEN)
So now to make a long story short, the EVAP purge solenoid valve is located on the drivers side of the engine about 3" in front of the starter I can't get a good picture of it but its black, about 4" long and is directly in line with your master cylinder. You can get to it from up top, you will notice it has a red connector on it, I simply unplugged mine to keep the valve from purging to see if my stalling was related the EVAP system and all my symptoms went away. I wouldn't recommend keeping it unplugged, this is simply a way to troubleshoot when you are at your wits end. I haven't had the following TSB done to my truck so I don't want to say go ahead and bring your truck in for THIS particular TSB until I know it works from personal experience. I will in fact bring it there next week so I will update this thread in a few days. But below is the link to the exact TSB you can print out for your records, but don't bring in your truck until I have confirmed that this is in fact the problem!TSB Stalling
The reason I say this i sbecause I had a tune done from PCM for less and I am still having this problem. I do NOT believe the most up to date software from GM will get rid of this unless it is specifically addressed. I believe this EVAP setting is a variable that is not touched when the software is updated in the PCM. That is just my 2 cents, otherwise with my new PCM i wouldn't still be having this issue.