P1748 IS AN OBD II CODE. THIS CODE INDICATES THE PRESENCE OF AN ERROR CODE IN THE PCM. TRY TO RETRIEVE THE EQUIVALENT BMW ERROR CODE. IF U DON'T GET THE MANUFACTURER CODE IT'S GOING TO BE DIIFICULT TO SOLVE UR PROBLEM. CHECK THAT SPEED SENSOR AGAIN. IS IT OE??? MAY BE IT' DEFECTIVE. GOOD LUCK.