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Home >> GMC >> 2006 >> Envoy 4.2 S, 4WD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - 4.2L - DTC P0420 To P1682 >> DTC P0446 >> Circuit/System Testing

Circuit/System Testing

IMPORTANT: Refer to the J 41413-200  operation manual for detailed instructions. See Special Tools .
  1. Inspect the EVAP vent system for a restriction.
  2. Test the low reference circuit of the FTP sensor for an open or for high resistance.
  3. With the GE-41415-50  , connect the J 41413-200  to the fuel filler neck. See Special Tools .
  4. Start the engine.
  5. Allow the engine to idle.
  6. Use the Purge/Seal function to seal the system with a scan tool.
  7. Command the EVAP canister purge solenoid valve to 20 percent.
  8. Observe the vacuum/pressure gage on the J 41413-200  and the FTP parameter on the scan tool. See Special Tools .
  9. Allow the vacuum to increase on the gage of the J 41413-200  until it reaches approximately 16 inches H2O, or until the vacuum reached the abort limit on the scan tool. See Special Tools .
    • If the difference between the FTP parameter on a scan tool and the vacuum/pressure gage on the J 41413-200  was more than 1 inch, replace the FTP sensor. See Special Tools .
    • If the maximum Fuel Tank Pressure Sensor parameter on a scan tool display was less than 3.2 volts, replace the FTP sensor.
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