Nissan Repair: check engine light, serial communications port, oxygen sensors

Question
Von,
Hi there, I have a'96 nissan maxima with 124,000 miles on it, the check engine light came up about 3 wks ago and i had to change both oxygen sensors, on my way home yesterday, the speedometer stopped working and the check engine light came up again and i had to branch at autozone where i was told 3 things are wrong with it, the speed sensor, knock sensor and serial communication link malfunction. Can u please explain to me what all these are and if i can at least drive the car for a while before i get the resources to take it to the shop without any other thing being affected. Also, will this in anyway affect the car's overall performance? Thanks for your response.

Answer
Steve,

I thought I answered this one.  The speed sensor is vital since it tells the car how fast you are going.  The knock sensor lets the engine advance timing until the car pings and then backs off the timing.  The serial communications port is where they read the data from with their scanner.  Yes, you can drive the car since it is in limp mode but the gas mileage will suck.  Get the speed sensor and knock sensor and then reset the computer at your local Autozone or Checker.  If the codes will not reset then disconnect the battery for five minutes to clear the codes.