I got a brief warning light " Check Gauges " that appeared for one start up and then never reappeared .....but now I notice that my engine temp gauge is registering very low after 20 minutes of driving it is barely 140*. It has been spring like weather here in Tenn. so I am concerned. Usually after hwy driving it is dead center at 190*. No fluid lose...noted. Doc

 

Not knowing the age of your truck I would say the thermostat is bad. I remember reading on here that they are to fail open.

 

02... 5.9 HO Cummins...255K miles..water pump replaced at 170K. Can the thermostat be checked electrically or must it be removed?

 

You must remove it. It will probably be open when it should be closed. Purchase new one from cummins or dealer, part store brands are junk.

 

I just went through the same thing Put in a new t-stat and everything went back to normal. T-stat from dodge about $75.00

 

Put one in Christmas day....slick...24$ Advanced Auto...

 

Personally, I would buy one from Cummins and keep it under the seat.

 

The lift pump was a Cummins product....also junk..replaced it with a Raptor before it ruined another VP 44 on me....I am not brand loyal, but thanks anyway.

 

^^^That is a completely different issue^^^ . A non dodge or cummins t-stat will fail closed. Just went thru that and put back in the original t-stat when the one from napa failed.

https://www.dieseltruckresource.com/...t-t296207.html