Hi Dlondon V., Thanks for your feedback. It sounds like you're talking about a situation where the fuel cap on your car might affect the sensor and trigger a "check fuel cap" warning. If the cap is old but still functional, it might not necessarily warrant replacement unless it's causing the "check engine" light to come on. In such cases, simply ensuring the cap is securely tightened after refueling might resolve the issue without needing to replace it. However, if the cap is damaged or doesn't seal properly, it's best to replace it to avoid potential fuel system issues. Thank you for allowing us to resolve this issue as soon as possible. We are looking forward to do more business with you in the future.