2002 prius triangle....of death ?

Ok i have a 2002 prius and it has been running well as fa as I can tell. recently I had in highlight the red triangle of death and the multi display lit up. But I can hit in and continue to drive and use cruise control and everything. So I have not yet gone to autozone or anyplace to have the codes read. I am wondering if anyone else has seen thing where it will light the triabgle but not force cruise control to not work. Since I had the main battery rebuilt in april I dont think this is a battery problem and wondering if there is a reason it isnt constant. ?
aslo I am considering buying a scan gauge ll but was hoping somebody would anser my question that the scan guage ll can read and tell me the codes ?

 

i had recently within the last few months changed the non-working pump.... odd thinkg is I went to autozone and they either screwed up and accidently cleard the codes or the problem is very non-conistant. That was about 2 weeks ago. While there I bought a scan gauge and set it up yesterday. So far the codes are clear... just guess I wait till it happens again... shrug.