About a day or so after I posted this, the problem came back. Fans are back on, temp gauge is off, check engine light is on.

I'm going to try pulling the fuse again tonight to see if it works again. I know it'll be a temporary fix, but if it does correct the problem again, it seems like it must point to where the issue is. Does anyone know what pulling this fuse and running the for car awhile could change? Perhaps when the overly excited fans are disabled by pulling the fuse, the coolant is allowed to get back to a certain temp (maybe operating temp?), which kicks the PCM back into sending a signal to the gauge? I have no idea, just trying to throw some crazy ideas out there... any insight or other crazy ideas on this would be great. The gauge has given me problems off and on for years, usually it would go out any time I went on a long road trip, perhaps that is a clue too?

@ Massey:
Interestingly, pulling the 10 amp fuse definitely did work, and it worked for me exactly as described by two other people that posted previously: pulled the fuse, drove the car awhile, gauge suddenly went right to 210 and fans turned off, put fuse back, and everything worked right again, at least for a day or two. I didn't intentionally remove any corrosion on the contacts, but maybe some was knocked off by fiddling with it. I just assumed pulling this fuse somehow reset a sensor, or something, somewhere? I will check for corrosion at all of the contacts, as you suggested, to see if I can find any.

@ Marty:
Hmm, I did replace the CTS, and I don't think the original one was even bad, and that didn't fix my problem. I haven't gone for the thermostat yet. Don't know that I will, since it doesn't sound like a fix!

@ BigCat:
My thermostat is factory, so the temp is set at whatever setting the car is originally set to. I bought the car new, so I know it still has the factory thermostat.

 

If you still have the factory T-stat in you should think about replacing it. they should be replaced every few years, I do mine when I service my coolant. Since i remove the deathcool and put in the green stuff I service my cooling system every 2 years or so. Deathcool is supposed to be aevery 5 years.
The T-stat would not directly cause this issue but it could be part of the problem if it is stuck open.

Massey

 

Good idea. I need to service my cooling system, anyhow, so I'll go ahead and replace the thermostat while I'm at it.

By the way, I pulled that 10A fuse and ran the car awhile after my last post, and it fixed the problem again-- fans immediately went off, temperature gauge started reading again. However, this time it has remained fixed through two days of commuting and the check engine light has turned off (last time the gauge only worked about one day until it quit again and the fans came back on, plus the CE light never went off).

The amount of time it takes for the gauge to start working again with the fans disabled is about how long it takes for the car to reach operating temp... as if something is reset once the car is warmed up. That may be another clue to the problem? And I think cold weather is also a factor. This is such a weird problem. I'm still looking into what's triggering it and will post if I figure out an actual, non-temporary fix. If anyone else has any ideas, please let me know!

Thanks,
Selena

 

Yes this coincides with the computer wanting to retest the sensors. It will disreguard a faulty sensor and not process it's signals (hence the no gauge) then after a predetermined time the computer will attempt to drop out of open loop, durring this time it calls all sensors to respond. If it now reads the CTS then it will begin processing the signals (including the gauge) and put itself in closed loop. Normally closed loop is achieved once the engine reaches a certain temp that the CTS reports to the computer but it has to have a good cold reading before that can happen.

If you have already replaced the sensor and the same issue is present then I would look into things like I mentioned before like damaged wiring and corrosion. By you removing and replacing the fuse you can scrape off some of the corrosion and solve the issue. The fuse if it is a good quality one will have silver coating the leg so it will not corrode but the brass in the socket may. You may be solving your own issue by pulling and installing the fuse. Wouldn't it be nice if everything was that easy

Massey

 

Thanks for the advice. It's final's week, so the car's been put on hold for awhile (it's also still happily working since the last reset). I'm sure the problem will come back, so I'll thoroughly check the wiring, fuse, thermostat, etc. as you suggested once the holiday break starts. If I find anything definitive that fixes it, I'll post it here for anyone else that's having this problem.

Thanks,
Selena

 

I had this problem. The solution was to replace the thermostat. Apparently, the thermostat was stuck open. The computer checks the temperature after a few minutes of operating, and it sees that the temperature is too low, so it throws a check engine code, and it shuts off the signal to the temperature gauge. I think that it is stupid that it shuts off the signal to the temperature guage, it would be much easier to troubleshoot if you could see the actual temperature, and you would not go on a wild goose chase thinking that something is wrong with the temperature sender or gauge.

 

^^^ Thats great, bring back a 4 month dead thread.

The computer will not kill the signal to the gauge if the CTS is reading normal even if the temp is too low. If your car is doing that then you prolly have a bad CTS.

Massey

 

The reason that I brought it back to life is that this is the most prominent thread that I found when researching my problem. You don't think that I replaced the CTS and traced the wiring? All of the mechanics that I spoke to thought the same thing. On a technical forum for GM mechanics, this question was asked by my mechanic and the answer came back that the problem was the thermostat, and the computer stops sending a signal to the gauge. This car only has one CTS instead of two as some cars do, so not all cars act this way. As soon as we replaced the thermostat, and cleared the code, the temperature gauge worked again, and it has been about a month and I have had no more issues. If you look back in the thread, you will see that someone else's issue was fixed by changing the thermostat, but they erroneously thought that it was due to moving a connection. I posted this for anyone else in the future who might have this issue.

 

Thanks for the input luchenbach, and for reviving this thread. My car is still having this problem, mostly because school sucks up all of my free time. I haven't yet replaced my thermostat and this strengthens the case that I should. It's a relief to hear someone say they actually fixed this weird problem (seems rare, I know I haven't).

As for bringing back old threads, back in November I revived this one after it was dead for 9 months or so. To me that's a better idea than having multiple threads about the same thing over time. That way any of us can come back and post what we've found to help others in the thread having the same problem, and others using search engines can find a single thread with lots of input.

Selena

 

Well good luck with that... The thermostat is a mechanical device that has nothing to do with the computer or the sensor. All it does is hold the water in the block until it reaches a given temp. If it is stuck open then it takes longer to achieve proper temp, if it is stuck closed you over heat, if it is not there you take too long to reach temp just like if it were open. If you changed it and some thing started working that was not working before it is pure coincidence.

If it fixed your car good and I am happy you are up and running. Spiral if this works for you too then great. I will tell you replacing a thermostat has solved problems like not enough heat from the heater, a carb that vaporlocks, overheating, in vehicles I have repaired but one has never fixed a gauge not working right. (other than reading too low or too high)

Massey