Tahoe 2WD V8-5.3L (2007)
Fuel: Technical Service Bulletins
Fuel System - Switching Between Gasoline & E85 Fuel
Bulletin No.: 06-06-04-010E
Date: 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.
