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 pressures are not within range
  Refer to Fluid Pressure High or Low .
- Go to next step: If 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
  Replace the Q8 Control Solenoid Valve Assembly.
- Go to next step: If a pressure change does occur
Verify the conditions listed below do not exist. Carefully inspect each component for that condition. Repair or replace as necessary.

P0741 or P0742 - A/Trans Fluid Pump cover Assembly (219)

TCC Control Valve (227) stuck/sticking - debris, binding, damaged valve, or scored bore.
Converter Feed Limit Valve (220) stuck/sticking - debris, binding, damaged valve, or scored bore.
Pressure Regulator Valve (233) stuck/sticking - debris, binding, damaged valve, or scored bore.
Turbine Shaft Bushings (218), (228) damaged or loose.
Leak between stator/tower assembly and cover.

P0741 - 4-5-6 (w/Turbine Shaft) Housing Assembly (441)

TCC Turbine Shaft O-ring Seal (443) damaged or leaking.

P0741 - Torque Converter Assembly (1)

TCC friction material debonded or excessively worn.
One way stator clutch distressed.
Internal leak - missing or damaged seal.
Overheated due to lack of lubrication/cooler flow.

P0741 or P0742 - Lower Control Valve Body Assembly (351)

TCC Regulator Apply Valve (355) stuck/sticking - debris, binding, damaged valve, or scored bore. Bore plug (328) undersized or leaking.
Clutch Select Valve 2 (352) stuck/sticking - debris, binding, damaged valve, or scored bore.

P0741 or P0742 - Q8 Control Solenoid Valve Assembly (314)

TCM incorrectly reporting high OSS, causing early TCC apply or late TCC release.

P0742 - A/Trans Input and Output Speed Sensor Assembly (303)

Incorrect, high, OSS signal, causing early TCC apply or late TCC release.

P0741 - Control Solenoid Valve Assembly (21)

A/Trans Fluid Pump Seal Assembly (18) damaged or leaking.

P0741 - Torque Converter Diagnosis

Refer to No Torque Converter Clutch Apply .

P0742 - Torque Converter Diagnosis

Refer to No Torque Converter Clutch Release .