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, Tue, 3 Jan 2006 17:48:12
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Well, that was what originally made me think the dashboard gauge had an independent sensor somewhere; when I disconnected the sensor, I think the gauge remained where it was. With the information you provided though, that could have been because it stopped updating the conversion values via the ECM, when it went to the invalid value due to the open circuit. I know the scan tool just shows 206 degrees when it loses communication, so maybe that's just a default. It would have been interesting to observe the gauge while I was varying the values with my potentiometer (I could see the scan tool readings going up and down as I varied the resistance to simulate the temp sensor), but didn't think to try at the time. The pot I had on hand wasn't the ideal range, because it was a 10K pot, and a bit hard to control around the area of interest. I did make the fan cycle on and off as I varied it. Probably a 2K pot would have been ideal, since full hot was in the range of a couple hundred ohms, and room temp about 2K, the values I measured before.
Before I dug up a pot, I happened to have a 10k resistor, which I thought I'd try just to see what it does to the reading, but that was a mistake, because it tripped the P0118 DTC for ECT voltage high. I guess if it's not an open circuit, it recognizes the value is out of range compared to the ambient temperature- the ECM's no dummy- :-) Luckily it cleared itself out after running a while under the in-range conditions.
If the dash gauge gets its reading from the same sensor, then I'd lean towards the ECT sensor, especially since the scantool reading came back with a dubious value of over 210 degrees after a 2 hr cooldown in 40 degree ambient temperatures. My house should be so well insulated...
Seems like it's unlikely that the ECM is converting the values incorrectly, and though I didn't try verifying the >1k source resistance, I did confirm a 5V excitation output from the harness terminals.
It's kinda out of my hands at this point, because I couldn't get the part from the dealer, since they were closed for the holiday, and eeuroparts doesn't appear to stock the item- they do have the t-stat though, but I didn't order it because I didn't think the chances were good that would have fixed it. I couldn't find many online sources for the ECT sensor, except for Autozone, but they're special order only. Guess there's just not too much call for the things for some reason.
So, because he was rather pressed to get it working quickly as it's his only car, he's bringing it to a shop and they'll be taking it from there.
I'll try to find out what the end result is-
posted by 68.237.7...
, Tue, 3 Jan 2006 17:48:09, Tue, 3 Jan 2006 17:48:12, Fri, 6 Jan 2006 20:27:27
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