Nissan Repair: 94 Sentra Check Engine Light, sentra, blow out

Question
I was trying to clean out engine, drove for 10 miles in 2nd gear @ 35 mph - Check Engine Light (Automatic trans).  It has never come on before. 195,000 miles on car.  Any suggestions?

Answer
Cristna,

I would take the transmission connector off.  The electrical one and blow out the connection with comrpessed air.  Before I did it I would disconnect the battery.  After I was done I would reconnect the connector and the battery and see if that corrected the short.