I did this test two weeks ago but was busy so i,m posting it up now that I got the chance. Was poking along on here and Joe (Izzy351) had done this and I figured I never seen them posted here, thanks Joe. The test was just like Joe said, with the key off, push the trip button in and hold for about 30 seconds, then still holding the button, turn the key to the start position but don't crank it, then you can scrool thru and see the codes and such. I know it works on my 03, I think you can do it from 02-03 if I remember correctly, here we go, these were on my truck.>> Check bulbs and dash lights, the whole dash lit up. PF3346,SF0E09,0284475,19NIN6,R0503,17R0503,EE01,DT 3831,CF160,CF200,CF300,CF400,DTC9352 AND FLASHING,EN6000,RIC000,EAC0000,F233,FP253,234C,OIL 233,073EF,BR123,BATTERY12.6,RIE00,PRND40,PAR WITH A DIAMOND SHAPE NEXT TO IT,D00Z00,STBT9,CHE01,PA80,PB11,PG1C,P620,PH90,PPD 8,P58-9F FLICKERING BETWEEN 8-9,PT25,PCANSF,AD0000,AD1 24767-8 FLICKERING BETWEEN7-8, AD2246-7FLICKERING BETWEEN6-7,AD3076-7, FLICKERING BETWEEN6-7,AD4-146,AD5-234,AD6-160,AD7-146,GAUGE CHECK, very interesting, found out my volts were 12.6, oil was 233* if thats correct, seems kinda high but still learning.. Pick it apart if you can and try it out on your truck.