Well even though it may not tell why its slipping, liek you said it will show me if the solenoids are workin and all. I dont actually have a check engine light right now nor does the topaz, but it would be nice to have one and be able to see if there is anything going wrong like the O2 which will not show a code unless it is completely dead. I dont have a problem with KR as Im N/A'd but I do know a few other people with older GM and Ford cars and they would be interested in this as well as I am. I think Im gonna order it tomorrow night after work. Ill let yall know how it turns out.