Hi, on the 2003 you hold the trip reset button and turn ignition on (No need to start engine) Hold it for approx 5 secs and let go, the needles will do a full sweep and test will be displayed, each time you press the reset button it will show new information, eventually it will flash dtc then the next set of codes, if any will be the dtc codes. Its pretty crude and nowhere as good as an obd2 reader but can be useful.

Hope this helps

Ian