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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 P077B >> 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. Operate the vehicle at 16-32 km/h (10-20 mph) while observing the Transmission Data Output Shaft Direction parameter on the scan tool.
    • If the Output Shaft Direction parameter corresponds with the vehicle direction and DTC P077B is set in the HPCM and not the TCM, replace the HPCM.
    • If DTC P077B is also set in the TCM continue testing.
  2. Disconnect the OSS connector.
  3. 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 greater than 9.3 volts, test the OSS supply voltage circuit for a short to voltage.
  4. Perform the Control Solenoid Valve and Transmission Control Module Assembly Output Shaft Speed Input Test .
    • If the OSS signal is not within the specified range, test the 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 OSS signal 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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