Can anyone help me?

I have a 1991 Honda Accord. There is a green "S" light on the dash to indicate overdrive which is activated from the shifter. This green "S" light (S for sport) is flashing repeatedly once you put the car in gear. In addition, the speedometer, odometer, and trip meter all stopped working and the "Check Engine" light comes on after 5 minutes and does not go off. Once you shut the car off and restart it everything is fine for a couple of minutes and then the process restarts again. I tried disconnecting the negative batery cable to clear the codes but the problem keeps returning. My QUESTION is: will a broken speedometer and odometer cause the check engine light to go on in this car. It would seem VERY coincidental that all 3 of these problems would happen at the same time. Also would the malfunctioning speedometer cause the overdrive light to flash incessintly. Thanks for any help that anyone can provide.

It is very possible that a broken speedometer cable might cause the symptoms you describe. I had a 92 Isuzu Trooper that had a speedometer cable which intermittently stuck which caused all kinds of other problems when the speedo wasn't working. Apparently the engine computer makes adjustments based on vehicle speed and when it wasn't getting a reading it made incorrect adjustments to the engine management which caused numerous drivability issues. Since the Check Engine light predominantly reports emissions control problems it is quite possible that the engine computer thinks that the emissions levels are out of the range they should be when going "zero" MPH as your speedometer is reporting. I would suggest fixing the speedometer and see if the other problems clear up, I suspect they will. You could also have the Check Engine code read (Auto Zone will do it for free) and see if the code supports my theory.