Water temp. gauge Q.

[LEADFOOT]

After I installed my headers, my temp gauge is not working right. I had to remove it for the install, I didn't do any thing to it to harm it. When I start the truck the gauge works. Shortly after it goes down like you shut the truck off. If I turn the truck off and wait about 15 seconds, and then turn the key to run but not start it, it will stay working, when I start it about a few seconds later it goes down again. I had a plug wire right up against it and thought that it was getting some RF interference. I have moved the plug wire and it still does it. WTF. Any body had this problem before? HELP PLEASE.

[XxInFaxX]

bad ground?

[LEADFOOT]

But it has 2 wires going to it so it shouldn't need a ground right? I put teflon thread tape on the threads when I put it back in.

[XxInFaxX]

im not really sure what the wires are that are going to it. i just mentioned the ground on the symptoms you gave. more electrical background speaking then car.

[Jake Nac]

Black wire is low reference; yellow wire coolant temp signal wire and the sensor should have a good ground itself.

[LEADFOOT]

I guess I should take the thread tape off.

[firefighter]

Makes sense but then it might leak did it have sealer on it when you took it out? I'm not sure but I think the sealer that they make for sensors and stuff is conductive at least I'm pretty sure the stuff GM made in the past was.

[firefighter]

I just looked for an old tube of the stuff and couldn't find one just check the auto parts though.

[LEADFOOT]

Yes it had some kind of sealer on it.

[firefighter]

I was just out and stopped at a auto parts and they have the stuff in the help section next to the teflon tape. Also try maybe using less tape so that the threads touch each other between sensor and head/block.

[LEADFOOT]

I will have to check at advance and see if they have that stuff. I hope thats the problem. If I turn the key to run and leave it there it will work right, but as soon as I start it a couple seconds later it goes down.

[Supercharged-ZQ8]

I will have to check at advance and see if they have that stuff. I hope thats the problem. If I turn the key to run and leave it there it will work right, but as soon as I start it a couple seconds later it goes down.
I don't think it's a ground problem -- if that were the case, it wouldn't work at all. This an intermittent thing. The sensor itself could be bad.

Try resetting the ECM. It you removed the sensor, but still had the battery connected, it may have screwed up the readings. If that is the case, resetting it should fix the problem. I don't mean reset it by disconnecting the battery, but by an actual "hard" reset: turn the key to "Run" so all the lights come on in the dash cluster. Remove the ECM1 and ECM2 fuses in the fusebox under the hood. Remove the keys and wait 10 seconds. Put the fuses back in, start it up and let it re-learn everything. It'll run like crap for a couple minutes (may even die), but once it picks up everything from the various sensors, it will go back to normal. Make sure you put it in drive, also -- it will probably die then also until it relearns what it needs to.

[LEADFOOT]

I got it fixed. Well actually I didn't fix it. I put my programmer on to see if I got any dtc's. Sure enough, 2 of them P0116(Engine coolant temp. circuit range/perf). And P0128(coolant temp below thermostat). Cleared the dtc's and whala, it works. I had the battery disconnected the whole time I was doing the install, except for the few times I had to hook it up to push it forward and open the back glass stuff like that. I don't know why the codes would have come up.

[OBI WAN]

Taking the sensor out allowed coolant to be displaced by air. Air trapped in these systems wont allow the temp to rise correctly. It may have burped itself out, but wont clear on its own until 3 cold starts and temp mins have been met! If it comes back, burp the system yourself. Cold take the cap off and run it until the Tstat opens up and the air will clear!

[bvr775]

I've never used teflon tape on temp sensors. I just smear a little copper sealer on them. i never though about it because I've never had the problem, but it makes cense if the tape is keeping it from getting a ground the gauge would go trough test mode and dye.

gm uses a liquid tread sealer on it. i don't know what GM calls it ,but i thinck it's like loc tight.