Circuit/System Testing

WARNING: This page is about a different car, the 2018 GMC Yukon XL, 2018 GMC Yukon, 2018 Chevrolet Tahoe, 2018 Chevrolet Suburban 3500 HD, and 2018 Chevrolet Suburban. However, it is still accessible from the selected car via links, so may be relevant.

Verify the transmission line pressures are within the specified ranges. Refer to Line Pressure Check .
- If line pressures are not within range
  Refer to Fluid Pressure High or Low .
- Go to next step: If line pressures are within range
Ignition OFF. Remove the Q8 Control Solenoid Valve Assembly.
Verify a pressure change occurs for each solenoid when performing the solenoid test. Refer to Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test .
- If a pressure change does not occur for each solenoid
  Replace the Q8 Control Solenoid Valve Assembly.
- Go to next step: If a pressure change does occur for each solenoid
Verify the mechanical conditions listed below do not exist. Carefully inspect each component for that condition. Repair or replace as necessary.

P0751 or P0752 - Lower Control Valve Body

Clutch select valve 2 stuck - debris, sediment, binding or scored bore or valve damage.

P0751 - Lower Control Valve Body

Bore Plug - Clutch Select Valve 2, Leaking, undersized bore plug, or damaged.

P0751 - Upper Control Valve Body

Check Ball #2 missing, damaged, or leaking.
Check Ball #2 Seat damaged or leaking.

P0751 or P0752 - Q8 Control Solenoid Valve Assembly

Shift Solenoid 1:

O-ring seals leaking.
Control signal fluid supply leak - valve body filter plate assembly cracked or damaged gasket seal.