Diagnostic Aids
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2012 GMC Yukon XL, 2012 GMC Yukon, 2012 Chevrolet Tahoe, 2012 Chevrolet Suburban, and 2012 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
- When an engine control module (ECM) is replaced or when the Fuel Composition Reset has been performed with a scan tool, the fuel system will need to contain ASTM gasoline with 10 percent or less ethanol content.
- If the fuel in the fuel system needs to be drained and replaced with ASTM gasoline, the engine will need to run at operating temperature and consume at least 1 liter (0.3 gallon) of fuel to flush out any remaining non-ASTM fuel. The fuel at the fuel rail will need to be rechecked to verify that 10 percent or less ethanol is now at the fuel rail. At this time the Fuel Composition Reset can be performed and will default to 3 percent.
- Resetting the system restores the vehicle to factory fill conditions and 10 percent or less ASTM gasoline must be present for future calculations. Resetting the system does not cause a relearn event to occur. The system will now be able to recognize the correct ethanol content in the future. Either ASTM gasoline or ASTM E85 fuel can then be used.