1. no, not really. If you don't hook up the speed sensor to the computer, you will get a code but it will not affect anything.
You will either need to run wires from the factory speed sensor to the speedometer or from a speed sensor that is compatible with your speedometer. Did your electronic speedo come with the sensor? My Autometer instructions said that it would work with the factory sender. I don't know about some of the others.
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