doubts with a code

I have just bought a 94 caravan, it has the light of the doors on and off every now and then, but some days ago it stopped and nothing worked. I changed the battery and worked fine for one hour but at one time it stopped, although this time I cold turn it on. The code that appears is 355. I know that 55 is the end of the serssion, but I don´t know if exsists a number 3.
When the car stops seconds earlier the light of check gage turns on. What do I have to check?

Thanks a lot