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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 506 (Automatic Transmission - 6L80/6L90 - Diagnostic Information And Procedures) >> Diagnostic Information and Procedures >> DTC P0756 >> Circuit/System Testing

Circuit/System Testing

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  1. Perform the Line Pressure Check . Verify the transmission line pressures are within the specified ranges.
    • If the line pressures are within the specified ranges 
  2. Ignition OFF, remove the Q8 control solenoid valve assembly. Refer to Control Solenoid Valve and Transmission Control Module Assembly Replacement .
  3. Perform the Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test . Test all solenoids on the Q8 control solenoid valve assembly. A pressure change should occur for each solenoid valve.
    • If a solenoid valve does not change pressure 

      Replace the Q8 control solenoid valve assembly.

    • If all solenoid valves change pressure 
  4. Listed in the chart below are conditions for each component that could set DTC P0756. Carefully inspect each component for that condition. Repair or replace as necessary.
DTC Component Condition
P0756 Lower Control Valve Body (351) Clutch select valve 3 stuck off - debris, sediment, binding or scored bore
P0756 Lower Control Valve Body (351) Bore Plug - Clutch Select Valve 3 leaking, undersized bore plug, damaged
P0756 Lower Control Valve Body (351)
  • Check Ball #3 missing, damaged, leaking
  • Check Ball #3 Spacer plate seat damaged, leaking
P0756 Q8 Control Solenoid Valve Assembly (314) Shift Solenoid (SS) 2:
  • O-ring seals leaking
  • Control signal fluid supply leak - valve body filter plate assembly cracked or damaged gasket seal
P0756 1-2-3-4 and 3-5-R Clutch Housing Assembly (51) 1-2-3-4 clutch backing plate retaining ring not seated, causing the piston to over travel and cut the 1-2-3-4 clutch piston seal
P0756 Fluid Pump Cover Assembly Fluid pump cover vanes and fluid pump rotor broken
P0756 Low Clutch Sprag Assembly Broken or incapable of holding torque
P0756 Pump Seal Seal is cut, torn causing a leak due to pump speed and capacity
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