All I've done with the regulator is remove the drain plug. I didn't get any tar out of the regulator. This truck has 9k hrs. Probably well over life expectency of the regulaor.New customer for us & their maintenance has been doing planned maintenance & repairs they can handle.Another tech tried linking up Spectrum software today & had no luck either. I sure would like to see what if any errors there are before we start replacing parts.

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.

I did mention a tune up to the customer but they dismissed the idea because the problem started so suddenly. I connected a co analyzer after changing O2 sensor. I had readings going up & down from.5 % to 2 %. I thought that was probably normal to fluctuate but I'm not familiar with the system. I wish I had taken a reading before for a base line.The complaint was truck set off a co detector in an office connected to the building they run the truck in.I'm going to push the tune up again.Can I just lean out the mixture by removing cap from screw on the mixer?

In the install folder of the spectrum software, there should be a 'readme' file, that has the code.
Some 'old school' to consider on this truck.
The computer makes it run even down to 3 cylinders before you recognize it as bad, spitting or popping.
An o2 sensor out of range does not mean the o2 sensor is bad, it means the truck is either running lean, or the exhaust has too much unburned gas. I would start with a -complete-tune up.
if the light is off and does not come back after pulling the battery cable, the cause of the warning light being on is now fixed.