"Let's assume for the sake of this answer that the defect is not safety-related. I am mindful that customers often have ideas that are very logical from their point of view, but may not take all the complications of an engine management system into account. First, I would analyze the data that the customer provided with their complaint. If they did not provide any, I would ask for some. If I concluded that their solution would not address the root cause of the problem, I am guessing that an alternate possibility would suggest itself to me as I looked at the data. I would write up my suggested solution and distill the two solutions down to a brief description of the problem, the problems with the customer's solution, how my solution would mitigate the complaint, and then ask my manager what approach would best meet our commitment to this customer. Going the extra mile without charge might be a good long-term strategy. On the other hand, we might be further ahead quoting my alternative if we think they will listen. If the power relationship is such that 'customer says frog, we jump,' then maybe it is better to just implement the customer's solution. I'd want to at least note in the documentation that we did not have full confidence that their solution would work. I would make my recommendation, but the strategy that is selected is up to my boss. Having registered my objections, I would then do as my boss asked, no matter how dumb I thought it was."