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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 145 (Engine Control System & Fuel - 4.8L, 5.3L, 6.0L And 6.2L - DTC P0335 To DTC P3449) >> DTC P0641 or P0651 >> Circuit/System Testing

Circuit/System Testing

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IMPORTANT: Additional DTCs may set when disconnecting components.
  1. Ignition OFF, disconnect the harness connector of all the sensors connected to the 5-volt reference bus for the applicable DTC. Refer to Circuit/System Description .
    2. IMPORTANT: A short to voltage on the signal circuit of certain components may cause this DTC to set.
  2. Ignition ON, test for 4.8-5.2 volts between one of the 5-volt reference circuits and ground.
    • If less than the specified range, test all of the 5-volt reference circuits for a short to ground. If all circuits test normal, replace the ECM.
    • If greater than the specified range, test for a short to voltage on all of the 5-volt reference circuits, or the signal circuit for each component associated with the appropriate 5-volt reference bus for a short to voltage. If all circuits test normal, replace the ECM.
  3. Connect each component associated with the appropriate 5-volt reference bus, one at a time, while monitoring the voltage. The voltage should not change more than 1 volt.
    • If the voltage display changes more than the specified range when a component is connected, replace the component.
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