Fuel System - Switching Between Gasoline And E85 Fuel
Bulletin No.: 06-06-04-010EDate: July 25, 2007
INFORMATION
Subject:
Information on 3.5L (VIN K - RPO LZE), 3.9L VIN W - RPO LGD) and 5.3L (VINs Z, 0, 3 - RPOs L59, LMG, LC9) E85 Fuel Compatible Vehicles - Alcohol Content, Switching Between Gasoline and E85 Fuel
Models:
2007 Buick Terraza
2006-2007 Chevrolet Avalanche, Impala, Monte Carlo, Silverado, Suburban, Tahoe
2007 Chevrolet Express, Silverado Classic, Uplander
2006-2007 GMC Sierra, Yukon, Yukon XL
2007 GMC Savana, Sierra Classic
2007 Pontiac Montana SV6 (Canada Only)
2007 Saturn Relay
with 3.5L, 3.9L or 5.3L E85 Compatible Engine (VINs K, W, Z, 0, 3 - RPOs ZLE, LGD, L59, LMG, LC9)
Supercede:
This bulletin is being revised to announce the release of calibrations for the 2007 full-size vans and classic trucks. Bulletin content and warranty information has also been updated to reflect this change. Please discard Corporate Bulletin Number 06-06-04-010D (Section 06 - Engine/Propulsion System).
For 2006, GM has changed the method of "sensing" the alcohol content of fuel in E85 compatible vehicles.
Only vehicles designated as E85 compatible are capable of operating on fuel with greater than 10% ethanol content. See Service Bulletin Number 05-06-04-035.
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.
A minimum of 11 Liters (3 gallons) must be put in the tank in order for the vehicle to identify/recognize a "re-fueling event." It is necessary to turn the ignition "off" in order to have the re-fueling event recognized; however local safety regulations should be followed.
The system is initialized by baselining itself on ASTM spec Gasoline (alcohol 0-10%). When an E85 compatible vehicle is built, an ECM or PCM replaced, or if the learned alcohol content has been reset with a scan tool, the fuel system will need to contain ASTM spec gasoline with 10% or less ethanol content. If the fuel in the fuel system needs to be drained and replaced with ASTM spec gasoline, the vehicle will need to run for approximately 11 km (7 mi) at full operating temperature before the system will be fully adjusted to the correct alcohol content. Once system initialization has been completed and the calibration verified to be the below listed calibration part number or later, gasoline with any ethanol content between 0 and 85% may be added, provided it is added in a quantity of 11 Liters (3 gallons) or more, and the vehicle is run long enough to learn the new fuel (see below).
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 02 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 02 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).
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.
If it is assured that only non-blended (containing E10 or less ethanol) gasoline is in the tank, then directly proceed with ECM programming.
Prior to reprogramming the ECM, the ethanol content must be determined. First record the ECM estimated value using the Tech2(R). Then check the actual percentage of alcohol (ethanol) in the fuel using J 44175 or J 44175-A.
If fuel was drained, it can now be returned to the vehicle as a "next fuel fill" provided that the amount is 11 Liters (3 gallons) or more and the ethanol content is between 0% and 85%.
Switching Between Gasoline and E85
No special precautions need to be taken when switching back and forth between gasoline and E85 other than re-fueling events must be 11 Liters (3 gallons) or greater, and the vehicle must remain in closed loop long enough (usually by the time the vehicle has been driven for 11 km (7 mi) at full operating temperature) to comprehend and calculate the composition of the new blend in the tank.
For best driveability, the vehicle should be driven for at least 11 km (7 mi) following a refueling event when switching between gasoline and E85.
Warranty Information
For vehicles repaired under warranty, use the table.
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