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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 P0776 or P0777 >> Circuit/System Testing

Circuit/System Testing

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    NOTE:

    You must perform the Circuit/System Verification first.

  1. Verify the transmission line pressures are within the specified ranges. Line Pressure Check .
    • If fluid 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 pressure change does not occur for each solenoid 

      Replace the Q8 control solenoid valve assembly.

    • If a pressure change occurs for each solenoid 
  4. Listed in the chart below, are conditions for each component that could set DTC P0776 or P0777. Carefully inspect each component for that condition. Repair or replace as necessary.
DTC P0776 or P0777

DTC Component Condition
P0776 Control Valve Upper Body Assembly (304) 3-5-R Regulator Valve (336) stuck / sticking - debris, binding, damaged valve, or scored bore
P0777 Control Valve Upper Body Assembly (304) B-2-6 Regulator Valve (334) stuck / sticking - debris, binding, damaged valve, or scored bore
P0776
P0777		 Q8 Control Solenoid Valve Assembly (314)
  • O-ring seals leaking
  • Valve body filter plate assembly cracked, blocked or damaged gasket seal
P0776
P0777		 Control Valve Upper Body Assembly (304)
  • Actuator feed limit circuit supply fluid to solenoids restricted or not available (debris or sediment blockage)
  • B-R-1 / 4-5-6 clutch regulator valve (327) not in the applied position - debris, binding, damaged valve, or scored bore
  • 4-5-6 clutch boost valve (329) not exhausting - debris, binding, damaged valve, or scored bore
P0776
P0777		 Torque Converter (w/Fluid Pump) Housing Assembly (2) Fluid pump housing vanes / rotor / slide damaged / scored
P0776
P0777		 A/Trans Fluid Pump Cover Assembly (219) Isolator valve (236) stuck / sticking - debris, binding, damaged valve, or scored bore
P0776 1-2-3-4 and 3-5-R Clutch Housing Assembly (51) 3-5-R clutch backing plate retaining ring (400) not seated
P0776
P0777		 1-2-3-4 and 3-5-R Clutch Housing Assembly (51) 1-2-3-4 clutch backing plate retaining ring (429) not seated, causing clutch pack / piston over travel
P0776 4-5-6 Hub / Shaft Assembly (58) 4-5-6 Hub / Shaft - broken hub weld
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