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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 361 (Automatic Transmission - 2ML70 - Diagnostic Information And Procedures) >> Diagnostic Information and Procedures >> DTC P079C >> Circuit/System Verification

Circuit/System Verification

WARNING: This page is about a different car, the 2011 GMC Yukon, 2011 Chevrolet Tahoe, and 2011 Cadillac Escalade. However, it is still accessible from the selected car via links, so may be relevant.
  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.
  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 P079C. Carefully inspect each component for that condition. Repair or replace as necessary.
DTC Component Condition
P079C Control Valve Body Upper Assembly (343) Hybrid Low, 1-2 Clutch Regulator Valve (336) stuck - debris, sediment, binding or scored bore
P079C Control Valve Body Upper Assembly (343) Valve Retaining Plug - Hybrid Low, 1-2 Clutch Regulator Valve, leaking, undersized bore plug, or damaged
P079C Control Valve Body Upper Assembly (343) Hybrid Low, 1-2 Clutch Boost Valve (337) stuck - debris, sediment, binding or scored bore
P079C Control Valve Body Upper Assembly (343) Shift Solenoid Valve - Mode A (328) stuck - debris, sediment, binding or scored bore
P079C Control Valve Body Upper Assembly (343) Shift Solenoid Valve - Mode B (332) stuck - debris, sediment, binding or scored bore
P079C Control Valve Channel Plate (304) Control Valve Channel Plate damaged or contaminated with large debris
P079C Control Solenoid Valve Assembly (307) Clutch Pressure Control Solenoid 3:
  • O-ring seals leaking
  • Control signal fluid supply leak - valve body filter plate assembly cracked or damaged gasket seal (307)
P079C A/Trans Fluid Pump Ball Check Valve (302) A/Trans Fluid Pump Ball Check Valve damaged, missing, or stuck
P079C 4th clutch assembly Slipping or damaged
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