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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 999 (Engine Controls - 4.8L, 5.3L, & 6.0L (Troubleshooting & Diagnosis)) >> Troubleshooting >> Alcohol/Contaminants-in-Fuel Diagnosis (with Special Tool) >> Test Procedure

Test Procedure

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
  1. Test the fuel composition using J 44175  Fuel Composition Tester and J 44175-3 Instruction Manual.
  2. If water appears in the fuel sample, perform the following steps:
    1. Clean the fuel system. Refer to Fuel System Cleaning .
    2. Replace the fuel filter if the vehicle is equipped with a serviceable fuel filter.
  3. Subtract 50 from the reading on the DMM in order to obtain the percentage of alcohol in the fuel sample. Refer to the examples in the Fuel Composition Test Examples table.
  4. If the non-blended gasoline fuel sample contains more than 15 percent ethanol, or if the E85 blended gasoline fuel sample contains more than 85 percent ethanol, add fresh, regular gasoline to the vehicle's fuel tank.
  5. Test the fuel composition.
  6. If additional testing indicates that the ethanol percentage is still more above 15 percent for a non-blended gasoline sample, drain and replace the vehicle's fuel. Refer to Fuel System Cleaning . If additional testing indicates that the E85 blended gasoline sample is still above 85 percent, continue adding fresh, regular gasoline until the ethanol content is 85 percent or less.
Fuel Composition Test Examples

- Frequency (Hz) Subtract 50 Ethanol Percent
Example A 50 Hz -50 0
Example B 65 Hz -50 15
Example C 129 Hz -50 79
Example D 135 Hz -50 85
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