Need help with engine questions

SEL-stop engine light. (red warning light.)
CEL-check engine light. (yellow warning light.)

When you turn motor off does your warning light also go out and how long before you have motor running does it come back on?
Have you checked level of coolant? Could be oil pressure or oil level. Not sure what sensors the stop engine light is wired for.

 

I have a N14 in my Freightliner. Not sure about the Dash lights in a Volvo.
They all should cycle on and off when you start your truck. I don't know how to check the codes on your truck. On mine I have a toggle switch I turn on and turn key to start but just enough to turn electrical system on, not actuate the starter. My red light blinks on and off, you count the number of times it flashes and that is your code.The sequence will give you three numbers than repeat. Here is a link for the fault codes. Good luck.

http://www.diesel-service-parts.com/celect-plus-codes.html

 

Your truck being an 02 you will have to put money into it. TLC money.
Did you have a mechanic look your truck over.
I had a Volvo with an N14 motor. The red engine light would ever so lightly flash on and off driving under a load. Took it several times to a shop to have it look at. Everything was always ok.
Until that one day it stayed on bright as could be. Before then the light would never come on bright, it would not stay on, usually only climbing hills under a load it would flicker lightly on and off. It never shut the motor down.
TO shorten the story it was low oil pressure/volume. Dash gauge wasn't accurate. My main bearings seized.
Lesson learned, I had a spare in the driveway and the first thing I did was have the oil pump changed. Cheap enough to have done and what a piece of mind it gave me.
Good Luck