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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 251 (Automatic Transmission - 2ML70 - DTC P0218 To DTC P0967) >> DTC P0721-P0723 >> Circuit/System Testing

Circuit/System Testing

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. Disconnect the OSS connector.
  2. Test for 8.3-9.3 volts between the OSS supply voltage circuit and ground.
    • If less than 8.3 volts, test the OSS supply voltage circuit for an open/high resistance or short to ground.
    • If the OSS supply voltage circuit tests normal, replace the control solenoid (w/body and TCM) valve assembly.
    • If greater than 9.3 volts, test the OSS supply voltage circuit for a short to voltage.
  3. Using a terminal test kit, connect the red lead of J 38522  to the OSS signal circuit terminal B and the black lead to the OSS supply voltage circuit terminal A.
  4. Set the J 38522  Signal to 8 volts, the Frequency to 120 and the Percent Duty Cycle to 50.
  5. With the ignition ON, observe the Transmission OSS parameter, The Transmission OSS parameter should display between 100-400 RPM.
    • If the Transmission OSS is not within the specified range, test the Transmission OSS signal circuit for an open/high resistance, short to ground, or a short to voltage.
    • If the circuit tests normal, replace the control solenoid (w/body and TCM) valve assembly.
    • If the Transmission OSS is within the specified range, visually inspect the OSS and the output shaft machined surface for damage or misalignment. If OK, replace the OSS.
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