Need some serious help with identifying a problem!!

[HarleyEberly]

So today I just bought a bmw z4 3.0 with 148,000 miles. My mechanic and I test drove it two days ago and he looked over the whole car and used his scanner to see if it had any problems and couldn't find any besides the radiator leaking a bit. So i cashed my loan check and bought it officially today and drove it home perfectly fine, but after i parked at my house then went to my friends house the light for transmission came on(one with the gear and an exclamation point inside it). Then it started revving high before going anywhere and i noticed when driving that there was some heat from right below the steering wheel. So I called my mechanic and he said to try driving in manual mode and see if it still does it. And so I tried it and it doesn't have that problem at all but i still feel some heat under the steering wheel but not as much. He is going to come take a look at it tomorrow and so i looked online and someone said it is the transmission valve not the transmission. I am hoping i don't need a new transmission as that would suck to need something so major the first day of buying it. And note this is from a private seller so no warranty or anything. Any help would be very much appreciated.

[MIKYZZ4]

Hopefully the mechanic used something more useful than a generic OBD2 scan tool,
Like INPA Software or even the Carly App for BMW which can communicate with all BMW computers,
and display real BMW error codes, unlike generic P-codes. I hope your mechanic is familiar with BMWs,
and the required diagnostic tools.

[HarleyEberly]

Yeah my mechanic has the big scanner that says exactly what the codes are and can run diagnostics and such.