The alternator was my first thought when she was having starting issues, so I had it tested before and after I replaced the battery and it was good. But as far as the CEL/MIL light, I haven't noticed it when driving and she hasn't mentioned any lights on before either. I've also checked fuses but that is the limit of my knowledge of electrical issues. I know to check the battery and it's terminals, alternator, and fuses. It seems that everything in the cab and on the exterior work fine from an electrical standpoint but the engine is different and I am lost.