when you pull the codes, is there a break in between when it throws the 15 blinks and the 4 blinks? because that could be it throwing 2 diff codes, and you got 15 short blinks? that is weird cause usually a 15 code will be one long blink worth 10 and 5 short worth 1 each.... but as for the tranny, since its a 5spd it wont really "go out" like a auto would with the torque converter, just parts like clutch, flywheel, bearings or synchros that can be fixed.....