98 DI, 153,000 miles, 60000 mile service done yearly, been running fine, cel is on and the only code stored is p0116............"engine coolant temp circuit range/performance"
checked all "visible " wiring & fuses, cleared the code.....but it came back immeadiately upon restart, it didnt matter whether the engine was cold or warmed up....if the code was cleared it would come right back.

decided to replace the coolant temp sensor with new one from at/british , cleared the code...same thing-- right back

coolant is full in rad as well as overflow tank, temp gauge on dash always reads in the "ok" zone, vehicle seems to warm up ok, thermostat was replaced about a year ago, .....

other than tearing into the wiring i'm out of ideas.....
heres hoping some one's crystall ball is working !
thanks

 

Try bleeding the system to make sure you don't have air trapped in the system.

 

THANKS MIKE..........
I'll give that a try and come back with the results

 

Well...bled the coolant system and all seems ok with that....cleared the code but again it came right back......
now Im on a mission. any other thoughts ?
thanks

 

Thought I would get back here with what I hope is the last chapter in this....I double checked the original temp sender and yup, it's junk, I checked the new one installed in the vehicle with my ohm meter as the truck warmed up and yup...it's working.
Now the fun starts.......I traced the two wires from the sender and the green one goes diredtly to the ecu--- checked continuity from one end to the other..all ok
the red /blk wire tees to a group of red /blk wires and I "sort of " traced them to the ecu and checked continuity... all ok, checked the connectors at the ecu and all appeared to be ok. I was ready to start looking for a new or used ecu...but put it all back together..cleared the stored p0116 code and also a pending p0116 code....started her up and praise be !!!! the cel is off !!! must have also had a poor connection some where as well as a bad sender but found no smoking gun. heres hoping this is the end of that !