Service manuals.

What type of truck

 

manualslib.com

 

Type of truck and engine would help. For the engine side of things, if you have a Cummins you can sign up for a free online shop manual using your engine serial number called quick-serve.

 

The software you are asking about, to check the dash lights (BTW it is an instrument panel, dashboards went out with the 1905 Curved Dash Oldsmobile) is proprietary, and very expensive. Manufacturers intentionally keep it as exclusive as possible so you have to go to them for the codes, hence the repairs. We are talking multiple $'s of dollars, specialized computer to run it on. These days, the dealers don't even have the software, they log onto the manufacturer server. You have to be an authorized dealer for that. Some independent repair shops, places like Penske/Ryder also have access, but pay for it dearly.
Service manuals are probably available in CD format, but will not have the information about the codes.

 

I have the Detroit software, $650 a year, and no specialized computer. Just a 9 year old Dell from Office Depot. I just ordered all the service manuals for my engine, and within them is any and every code possible and the troubleshooting steps to correct them.

 

I have access to DTNA Connect:
DTNAConnect - Daimler Trucks North America
which allows me to look at the parts book for my specific truck, not any other serial number. If you own your truck, you can get the same access. It is free, you just have to jump through some hoops to get it. The website above will spell it out for you. DTNA has requirements with the operating system on the computer, I had to upgrade to Windows 10 in order to access them.
The parts book is very handy, lots of detailed drawings, exact part numbers. Dealers love me when I ask for a specific part number instead of them spending 10 minutes,
" well it is kind of attached to the horsedoopy thing, yeah, but bigger than that, and it looks like it has some right hand threads, no left hand threads....
You get the drift, if you have spent any time at any parts counter.

 

YEs you get access to dtna connect wich includes parts pro but thats pretty much it. To get access to software to read codes from your truck and troubleshoot them, you need to go to any frightliner dealer and ask them to send a request to dtna head office saying that they don't mind if you get the access. Stupid I know