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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 237 (Engine Control System & Fuel - 4.8L, 5.3L, 6.0L, Or 6.2L - Troubleshooting & Diagnosis) >> Fuel Composition Diagnosis >> System Description

System Description

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When an E85 compatible vehicle is built, an ECM or PCM replaced, or when the learned alcohol content has been reset 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 of fuel before the system will recognize the correct alcohol content. Either ASTM gasoline or ASTM E85 fuel can then be used

Step Action Values Yes No
1 Did you perform the Diagnostic System Check - Vehicle? - Go to Step 2  Go to Diagnostic System Check - Vehicle (without HP2) or Diagnostic System Check - Vehicle (with HP2)
2
  1. Measure the ethanol content with a fuel sample from the fuel rail using the J 44175  Fuel Composition Tester. See Special Tools .
  2. Compare the measured ethanol content to the fuel alcohol content parameter on the scan tool.
Is the difference between the measured ethanol content and the scan tool fuel alcohol content more than the specified value?		 15% Go to Step 3  Go to Step 7 
3 Is the measured ethanol content less than the specified value? 15% Go to Step 5  Go to Step 4 
4
  1. Drain the fuel tank. Refer to Fuel Tank Draining (Single Tank) or Fuel Tank Draining (Dual Tanks - Front) or Fuel Tank Draining (Dual Tanks - Rear) .
  2. Clean the fuel system. Refer to Fuel Tank Replacement (1500 SWB - 98.4L (26 gal) Tank) or Fuel Tank Replacement (1500 LWB - 117.3L (31 gal) Tank) or Fuel Tank Replacement (1500 SWB - 98.4L (26 gal) Tank + E85) or Fuel Tank Replacement (1500 LWB - 117.3L (31 gal) Tank + E85) or Fuel Tank Replacement (2500 LWB - 98.4L (26 gal) Tank-Front) or Fuel Tank Replacement (2500 LWB - 43.5L (11.5 gal) Tank-Rear) and Fuel Injection Fuel Rail Assembly Replacement .
  3. Add fuel containing 10 percent or less ethanol content.
  4. Operate the vehicle until at least 1 liter of fuel is used.
  5. Measure the actual ethanol content with a fuel sample from the fuel rail using the J 44175  . See Special Tools .
Is the measured ethanol content more than the specified value?		 15% - Go to Step 5 
5 Use the scan tool to reset the learned fuel composition to the specified value.
Is the action complete?		 3% Go to Step 6  -
6 Use the scan tool reset the fuel trim values.
Is the action complete?		 - Go to Step 7  -
7 Observe the Capture Info with a scan tool.
Are there any DTCs that have not been diagnosed?		 - Go to Diagnostic Trouble Code (DTC) List - Vehicle System OK
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