I need some help. This relates to my other thread about joining boards, because I can't seem to join any Jeep boards due to only having hotmail/yahoo/gmail accounts. Anyways, here's my problem. My brother took my dad's 03 grand cherokee (6 cyl, 4wd) up to tahoe over the weekend, and now the CEL is on. He's an idiot when it comes to automotive stuff, so he doesn't have any clue what happened or what was happening when the light came on. Does anyone know how to check the code, if it's even possible without a code reader? Either that, or somewhere I can find out how...because I haven't found anything yet.

TIA.