s-10 help

[beto101]

i have a 2001 s-10 blazer with a 4.3 4wd. i have a temp sensor code po117- engine coolant temp circuit low imput. i have replaced the sensor and still same problem. the temp gauge and rpm gauge both jump up and down. then sometimes it acts normal. Any ideas what could be causing this?

 

[thatK30guy]

My '98 Jimmy does the same thing but the tach quit working.

It also has a mysterious disappearing anti-freeze problem. No clue where its going. No spills, drips, leaks and no white smoke out the exhaust, etc. Nothing.

Same 4.3 as yours.