Spn code on dash after fix

I'm just an amateur o/o that can fix minor/moderate problems, but don't have a computer for the truck.

I bought a freightliner 2013 with a dd15 back in September. So far I did 2 repairs. Once a water hose was leaking got a new once and replaced it. At the time I got some spn codes cause of water level low etc. Codes went off on their own. Then while I was in Maine at -20 I got a spn 4354 line heat 1. I checked the heater once in warm weather and is working fine, but the code remains on dash. I got a truck wash about a week ago and when I got out I got 2 oil pressure spn codes on. The sensor cracked I went to freightliner and got a new sensor and installed it. Oil pressure was thenmagically back. But the codes are still there even though I know it got fix. Of the 2 oil pressure codes 1 went off on its own after a week and the other is still seating. Spn 100 17. Do I need to find someone with a computer to get the codes out or is there any other way?

Also I got a spn 841 code that I don't know what it is:
System 017 SPN 841 02

Thanks in advance!

 

Ok thanks.

And what does code spn 841 mean. That code does not trigger a check engine light, it was there before the heater and oil pressure problems happened.

 

The 10 min reset didn't work. It was more like 30 min all codes are still there. When I get home I'll call a friend that knows someone that got a computer. Hopefully he doesn't charge me too much to hook it up.

 

Found spn 841. An error with the truck gps, I think I can live with that

 

I got away with plugging the computer. Yesterday my engine break stoped working. So I started checking all cables etc. I saw the computer under the cup holders and unplugged all cables and plugged them back, didn't fix the jet brake but it took away all faults! Later I found the problem with the engine break, the dash light burn somehow and didn't close the circuit, replaced the light and is working fine now. So I did two for one

 

It reads exactly:

System 017 SPN 841 02

Which I believe is the gps. It came with an on guard unit that I have it remove and that might be the root of that.