Nissan Sentra 1993 crank but it wont't start

Hello I hope you can help me with this, I was driving my Nissan sentra 93 when it suddenly stop working, so I check the gas pressure, the spark, and everything seems like normal, like I said it cranks but it won?t start I just try to check the computer codes but it just give me 55 and it means anything is register by the computer. I don?t know what?s wrong whit it, also I try whit neutral but no results.