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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1998 (Engine Controls And Fuel - 3.6L (LCS) - DTC P0638 To DTC P2229) >> DTC P0641-P0643, P0651-P0653, or P0697-P0699 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2009 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, open the hood to disable the Auto-Stop function.
  2. Ignition ON, verify the scan tool hood position parameter displays Open.
    • If the hood position does not display Open, refer to DTC P254F .
    3. NOTE: Additional DTCs will set when disconnecting the components.
  3. Ignition OFF, disconnect the harness connector of all appropriate sensors for the applicable DTC. Refer to Diagnostic Aids.
  4. Ignition ON, test for 4.6-5.4 V between one of the 5-volt reference circuits and ground.
    • If less than the specified range, test for a short to ground on all the 5-volt reference circuits. If all circuits test normal, replace the ECM.
    • If greater than the specified range, test for a short to voltage on all the 5-volt reference circuits for each component associated with the appropriate 5-volt reference circuit. If all circuits test normal, replace the ECM.
    5. NOTE: A short to voltage on the signal circuit of certain components may cause this DTC to set.
  5. Connect each component associated with the 5-volt reference circuit one at a time while monitoring the appropriate scan tool 5-Volt Reference Circuit Status parameter. The parameter should continue to display OK.
    • If the parameter displays Fault when a component is connected, test the signal circuit of that component for a short to voltage. If the circuit tests normal, replace the component.
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