Greetings everyone,

I replaced the driver's door handle on my daughters Sentra over the weekend, and ever since then a "Key system error" is displayed on the dash. Does the vehicle need to learn this new hardware (handle)?

No, but there's a "door request" NATS antenna embedded in the handle. There should have been two connectors to the handle, one for the request button and another for the antenna. If the antenna connector is disconnected or has a problem, you'll get an "I-key System" warning. Should be a Gray 2-pin connector with Pink and Violet wires.