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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 505 (Automatic Transmission - 2ML70 - Diagnostic Information And Procedures) >> Diagnostic Information and Procedures >> DTC P079B >> Circuit/System Verification

Circuit/System Verification

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  1. Verify that DTCs P0721, P0722, P0723, P0966, P0967, P0969, P0970, P0971, P0973, P0974, P0976, P0977, P2720, P2721, P2728, P2729, or P2730 is not set.
  2. Perform the Transmission Fluid Level and Condition Check  to verify correct fluid level and condition.
  3. Perform the Line Pressure Check  to verify correct oil pressure.
  4. Perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection  to verify Q8 control solenoid valve assembly condition.
  5. Perform the Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test  to verify Q8 control solenoid valve assembly function.
  6. Listed in the chart below are conditions for each component that could set DTC P079B. Carefully inspect each component for that condition. Repair or replace as necessary.
DTC Component Condition
P079B Control Valve Body Upper Assembly (343) Hybrid Direct 2-3-4 Clutch Regulator Valve (326) stuck - debris, sediment, binding or scored bore
P079B Control Valve Body Upper Assembly (343) Valve Retaining Plug - Hybrid Direct 2-3-4 Clutch Regulator Valve, leaking, undersized bore plug, or damaged
P079B Control Valve Body Upper Assembly (343) #1 ball check valve, missing or damaged. Ball does not move freely
P079B Control Valve Body Upper Assembly (343) Shift Solenoid Valve - Mode A (328) stuck - debris, sediment, binding or scored bore
P079B Control Valve Body Upper Assembly (343) Shift Solenoid Valve - Mode B (332) stuck - debris, sediment, binding or scored bore
P079B Control Valve Channel Plate (304) Control Valve Channel Plate damaged or contaminated with large debris
P079B Control Solenoid Valve Assembly (307) Clutch Pressure Control Solenoid 2:
  • O-ring seals leaking
  • Control signal fluid supply leak - valve body filter plate assembly cracked or damaged gasket seal (307)
P079B A/Trans Fluid Pump Ball Check Valve (302) A/Trans Fluid Pump Ball Check Valve damaged, missing, or stuck
P079B Hybrid Direct, 2-3-4 Clutch Worn, damaged, leaking seals
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