The red CHECK ENGINE light on the dash can be a blessing, a curse, or both at the same time. If it comes on in the middle of nowhere when your customer is into the second week of a 3000 mile vacation trip, it’s definitely a curse. But if it can help you understand more about what’s going on under the hood, I’d call it a blessing. If it gives you incomplete or incorrect information, then I’d call that a blessing and a curse.