4T80E MH1 SES Light On DTC P0741 DTC 39 (TCC Stuck Off) - kw apply converter fluid MIL pressure shift slip stuck torque transmission valve

The following diagnosis might be helpful if the vehicle exhibits the symptom described in the PI.

Customer may complain of SES light on, SES light on and chuggle or surge. Diagnostics may show Excessive TCC Slip Speed, TCC may have partial apply fluid pressure or no apply fluid pressure and DTC P0741or DTC 39 will be a current code .

If excessive slip speed noted and condition/cause cannot be diagnosed by using DTC P0741or DTC 39 diagnostic chart, inspect for worn seals causing slippage of the drive sprocket bearing inner race on the drive sprocket. The inspection requires the transmission be removed from the vehicle (SI reference for trans removal). Remove the side cover, upper valve body, case cover, drive chain, drive and driven gear. Inspect the drive sprocket support for wear on the outer radius. Inspect the following seals for wear:

Seal, Case cover to drive sprocket

Seal, Case cover to turbine shaft

The wear pattern will appear as an uneven appearance of the inner diameter white seal surface, in some instances the inner seal may be torn away from the seal shell or the seal surface may be uneven in appearance. Compare a new seal versus the installed seal . The white seal surface should be even in width around the inner diameter. Seal damage will allow TCC apply fluid to drain into the channel plate, causing excessive slippage of the TCC under certain load conditions and eventually cause no TCC apply. In addition the following seals should be replaced.

Drive sprocket oil seal

Seal, turbine shaft O-Ring

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Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance.

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