there is no code for battery recently disconnected, there is a p1000 code wich will set if the battery is disconnected, but only because the OBD drive cycle clears and all the monitors will have to run again to clear the p1000. this will also happen if codes are cleared. if the codes come back after clearing, then you have a fault, its not that the sensors arent "registering". like i said, if your mechanic is telling you to drive it to clear the codes then u need a new mechanic. part 2 if you cant pull out of s gear with the clutch depressed then you for sure have a internal trans concern, on a crrecrtly functioning trans you should be able to shift out of a gear at any time, you may not be able to shift into a gear due to road speed, but out always.