Mcuadra86 no problem have you replaced it yet and if so has it fixed your problem

Malibu temperature sensor problem
 

I have the same problem. FYI if the temp sensor is cold the AC will not cycle on. The issue is with the sensor circuit. I replaced the sensor; it worked for a few days and failed again. It may be a wiring problem which I will check but I suspect it is a ECM problem.

If anyone knows let us have it; it appears to be a common problem.

Malibu temperature sensor problem
 

The thermostat has nothing to do with this issue. The coolant temp sensor feed data to the ecm. If the temp sensor says t's cold the AC will not cycle on. I have the same issue and have changed the temp sensor but still have he problem. Will check wire next. Probably an ecm problem.

that seems logical.

I wanted to know for sure what conditions the pcm will shut off the a/c based on information from the ect sensor. All I could find however was pcm logic to shut off the a/c only during an overheating condition. As fas as I can tell...the pcm uses the a/c pressure sensor information to shut down the a/c to prevent evap freezing.

I am having the same issue. Things I have done: Changed ECTS, Thermostat. Removed Cables from PCM and applied Dioeltric Grease (which removing the cables reset the pcm and all was well for 24 hours) Removed and replaced PCM fuses which reset and all was well for about 24 hours. My mechanic is leaning toward the issue being a bad PCM. Has anyone come up with a solution to this problem?

The thermostat has nothing to do with this issue. If it is not the coolant temp sensor then it is wiring or the ECM. I replaced my temp sensor and problem came back. I can disconnect the battery when the gauge is not working and it will start working for a while. I'm sure it is my ECM and are now determining if I'm going to replace it on a 150K miles car.

when the problem is active what ya get when you check the 5volt ref to the ect sensor and low ref grd back to the ecm?

Temperature gauge not working
 

More data. When car sets overnight, outside temp 60s, the gauge will work until engine reaches normal temp then stop on way to work. Gauge will not work again until coming home after car reaches normal temp, outside temp 80s. Has to be ECM.

RockAuto has ECM for $160. I assume it has to be programmed by dealer?
Does anyone have experience with aftermarket PCM?

it will need to be reprogrammed or the car won't start.

its pretty easy to check the ecm supply voltage; verify the power and grd wiring cause every once in a while you will get caught.

Are you setting code po128? At work we take care of a fleet of city police cars. Replace the thermostat with a dealer stat and clear the code it will fix it. Trust me. I have seen this many times. You must use a factory t-stat. The code is referring to the car not heating up fast enough. For some dumb reason the pcm disables the temperature gauge and air conditioner. The reason it happens again after the temp has been in the 60 is the pcm re runs the test/monitor.

For all of you that do not believe me what do you have to lose $60 at most. When you pull it out you will likely see the stat is open slightly. It is far less then a computer.