2000 Honda Civic HX Engine Temperature Gauge Does Not Register?

There are 2 temperature sensors for the coolant on these things, if one is bad or has a corroded terminal, the gauge will not read and the computer will see that there is something wrong and set the light. If you have one sensor reading engine temp of 190 degrees and the other reads -40, then it knows something is wrong. It isn't sure what but it knows it isn't right.