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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 253 (Engine Control System & Fuel - Hybrid (Hp2) 6.0L (LFA) - DTC P0231 To DTC P0690) >> DTC P0641 or P0651 (Set in ECM) >> Circuit/System Testing (Set in ECM)

Circuit/System Testing (Set in ECM)

WARNING: This page is about a different car, the 2008 GMC Yukon and 2008 Chevrolet Tahoe. 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. Refer to Hybrid Modes of Operation Description .
  2. Ignition ON, verify the scan tool hood position parameter displays Open.
    3. IMPORTANT: A short to voltage on the signal circuit of certain components may cause this DTC to set.
  3. Ignition ON, disconnect the harness connector of all appropriate sensors for the applicable DTC. Refer to Diagnostic Aids for the appropriate sensors.
  4. Ignition ON, measure for 4.8-5.2 volts between one of the 5-volt reference circuits and ground.
    • If less than the specified range, test for a short to ground on all 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. If all circuits test normal, replace the ECM.
  5. Connect each component associated with the 5-volt reference circuit, one at a time, while monitoring the voltage. Verify the voltage remains between 4.8-5.2 volts.
    • If not within the specified range when a component is connected, test the signal circuit for a short to voltage. If the circuit tests normal, replace the appropriate component.
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