Welcome to the forum. If your datalink connector looks like the picture below, you may be able to access mil codes without special tools. You place a jumper wire between A & B terminals of the datalink connector. Turn the key just till the dash lites come on, no further, the mil starts flashing, you count the flashes to get the codes. example, a code 21, two quick flashes, slight pause, one flash. It should repeat three times before moving to next code, if there is one.