Ran a search but could not find what I was looking for. Have a new 2011 5.3 Silverado. If you run E85 Flex fuel does the ECM automatically vary the tune to accommodate. The owners manual indicates to just fill up and off you go but no less than 3 gallons.

 

The ECM calculates the E% and adjust the calibration to correct for the spark and fueling needs.

 

Pretty neat. Thanks!

 

For 2006 and 2007 models, E85 compatible vehicles marketed in North America no longer use an alcohol sensor to determine and adjust for the alcohol content of the fuel in the tank. Instead, the vehicle "learns" (calculates) the alcohol content of the fuel, (and subsequent mixture in the fuel tank), through a series of measured adjustments.

Adjustments

After the re-fueling event, the system registers the amount of fuel that was taken on-board, relative to the amount that was in the tank. Reading fuel trim and O2 sensor activity, the system determines the ethanol content of the fuel that was added. Based on that determination, it adjusts itself to the expected alcohol mix in the fuel tank and lets the fuel trim and O2 sensor activity fine tune the adjustments. The system must remain in closed loop in order for this adjustment to occur. Numerous short trips after switching from gasoline to E85, or vice versa, can result in driveability symptoms due to the inability of the system to adjust for fuel composition (by not attaining the parameters necessary to reach closed loop operation).

Important: GM has released revised calibrations for 2006 and 2007 model FlexFuel (E85 compatible) vehicles that will accept the introduction of gasoline/ethanol blended fuels with ANY ethanol concentration that falls between 0 and 85%.

The revised calibrations for these models are on TIS2WEB. Any of these models serviced for E85 related concerns should be checked to assure the engine control module (ECM) calibration is P/N 12614088 (new style full size trucks), P/N 12619631 or 12619632 (classic full size trucks), P/N 12619633 or 12619634 (full size vans) , P/N 12616453 (2006 Impala/Monte Carlo), P/N 12616478 (2007 Impala/Monte Carlo), or P/N 12611341 (2007 Montana/Relay/Terraza/Uplander) or later.



Important: If it is assured that only non-blended (containing E10 or less ethanol) gasoline is in the tank, then directly proceed with ECM programming.