My volvo drives and cuts off when I stop.what is the transmission related issue? on 2002 Volvo S60

The dashboard says I need to service my transmission. A new engine was just installed on the car.The transmission fluid has been changed, but the problem continues.
Do I have to buy another transmission or repair what is in the car?

Asked by for the 2002 Volvo S60
get a free diag and est from aamco then shop prices