Yes when Ace hooks up the ProLink it will tell if it has any codes to tell. But I have on more than one occasion with electronic engines had problems that did not signal a fault!
Just a week or so ago one of our members who has been busy with no bus projects went to take his bus from the storage to his new house w/bus barn.
It would start and run about 3-4 mins and die.
He called me and we went through the codes thing and all it was telling us was that it had a ECM Prom fault.
He called DD and they were of no help.
I talked to him again and had him check and make sure the plug on the ecm was plugged in good and the wires were not pulled out or shorted.
He did that an still did the same thing.
He asked "Will it hurt it if I just drive it until it shuts of, and pull over restart it and go again? I only have a short distance to go, like 5 miles".
I told him as long as it had oil, water and oil pressure I didn't see what it would hurt.
He called about 2o mins later and told me he made it home. Said it died 2 or 3 times and then just kept running all the way home and was sitting there doing fine now that it was home.
Never did find out what it was!
I also had on that had the infamous fuse issue and one day I got PO'd and yanked out the 2 injector inline fuse holders and replaced them and never had a problem again. (turned out the fuse holders had a lot of corrosion down in the slots and allowed bad connections!)