I have a 1999 Buick Lesabre that has a hard shifting problem but only sometimes. I put it on a computer diagnostic tester on it and it comes up with codes PO742 and PO1811, can you tell me what that entails, I was told it could be a pressure solenoid switch, where is that located and how hard is it to get to? thanks

P0742 TCC System Stuck On
P1811 Maximum Adapt and Long Shift