tune up may remedy the problem but there also could be an issue with the regulator, these trucks came with a series II cobra CS4-30772-004 and if the LP Gas gums up inside it this can cause the trim valve to malfunction giving a bad signal to the ecm also.
I'd pay attention to this as well, plus you will need to go into the diagnostic software and clear out any codes if they are still there. Unhooking the battery may remedy the code flashing temporarily but usually they come back until cleared out of the system. I've found at times these systems are sluggish when it comes to registering and sending codes to the display.
try the tuneup, check the regulator really good, clean it out if need be, run the software and clear codes and run the truck till hot for a while (at least 30 mins) to ensure everything has been remedied.