Check engine light comes on only when u start engine! Need help asap pleaseeee!!! S14
 

Hey guys! In trying to buy a 1995 240sx tomorrow and I guess it used to be an auto and it was swapped to manual but the guy is still using the stock auto ecu so obviously the check engine light is going to come on.

Now the problem is that I just found out that the check engine light is suppose to come on when u turn the key to the on position and then stay on when the car is started if there's something wrong.
Well with this 240, the check engine light does not come on when u turn the key to the on position but the light comes on after u actually start the engine and stays on.
So does anyone know why the cel might not come on when u turn the key to the on position but all the other lights do?
The oil light just stays on too.