Im new to diesels. I just bought my first a few days ago. It is a 2003 crew cab long bed 4x4. Yesterday i changed engine oil and filter, and also changed the oil and filter on the trans, everything looked good and went good. When i started it eveything sounded and looked good except the check engine light came on. i let it idle and warm up and checked the tranny fluid level it was good. shut it off and checked the engine oil level it was fine. so i started it back up and the check engine light was still on. Any ideas/