Temperature gauge not working on 2001 Malibu changed the temperature sending unit and still not working. Check engine light is on and code reads engine not reaching operating temp. What next?

Answer 1

I also have been fighting this demon. I've had the engine codes read and reset twice. I believe there is a short/bad connection on a harness somewhere. I've replaced the engine coolant temp sensor which didn't solve this problem. My temp gauge reads 0 and the coolant fans remain on constantly (both). My problem comes and goes however. I'll let you know what I find.

This is an update to my problem. I have installed a new coolant fan thermostat because now that it is Summer, my Malibu's coolant fans only operate when the air conditioner is turned on.
It didn't seem to fix my problem. My coolant gauge just decided to stay dead again. (it did however keep my car from overheating any more)

I had the same problem as the one above. I replaced the engine coolant temp sensor on 11/22/09 as my first try and still had the the problem. My next step was to replace the thermostat .... but first drain out at least 1/4 of the coolant. The thermostat removal was tough -- the top thermostat bolt on the cover is easy if you remove the nut and the two small little hoses on black piping bracket above in front of it and using a 13mm socket on a short extension go under the black pipe to remove top cover bolt -- not so hard at this step.

This next step was a nightmare, it was removing the bottom 13mm bolt on the thermostat cover. I made a couple of tools by cutting a junk 13mm open and closed end wrench in half to make a shorter set as there is no way with a long wrench - experiment on your own method here as there is not much room for hands or long tools especially if you don't have " EVERY TYPE TOOL IN THE WORLD. "

I put the new thermostat in and all else back together then refilled with Dexcool.

Note: be sure to purge air out of the coolant system - (1) loosen air purge cock ( about 1 or so turns ) located on front top pipe bolted on water pump passenger front side - as you are putting in coolant slowly during the circulating fluid process observe air purge cock outlet until all bubbles - air gone / coolant will be clear - bubble free. And also do not forget to re-tighten the air purge cock or over tighten it (brass).

(2) It's also a good idea too speed things up by removing one end of the small air return hose ON THE PLASTIC COOLANT TANK (just follow hose out from to top passenger side of radiator ) keep filling until full line on plastic tank is level then connect the hose back up - make sure too that air inlet pipe connection on / in plastic tank is not plugged up " (or cold) " as it will possibly break when removing this hose in the winter. Also, check tank level sensor for good connection on bottom. After all of this my engine light went out and thermostat temperature gauge works like new and my heater works better and hotter than the day I got the car.

I do not know if un-purged air trapped in cooling system will make this problem in someway later reoccur in case an inside pressure coolant sensor (??) is detecting low circulating fluid pressure from pump. If it does reoccur again for me (?) = I will update this article.