Location of coolant temp sensor?

2001 Impala LS 3.8L V6 -- Issue: Engine temp gauge reads as when off <140deg. -- CEL on. Otherwise the engine seems to be running normally, but the fans tend to stay on longer (even for a short time after shutdown), since the PCM cannot verify coolant temperature.

My guess is that either the sensor is bad or its cabling/harness may be loose.

So, where is it? I would expect to find it near the thermostat housing, but it does not appear to be there -- I wasn't able to get underneath to see if it's in one of the heads, or mounted low in the radiator.

I also assume that there's a resistance test I can perform on the sensor to determine if it is in fact reading out of range?

The ECT sensor is located a few inches below the t'stat housing... It's a bit rough to see or get a wrench on unless you remove some stuff around it first...

I also have a 2001 LS (3.8L) and had the same issue as you describe... I replaced the ECT and the t'stat and had to clear the DTC code twice before things went back to normal...

Thanks Gems :)

Are you saying that the ECT is easy to get to if I also remove the thermostat housing? Would I have to drain coolant first? I was considering doing the T-stat "soon" anyway, so I could kill two birds...

Another question -- T-stats: 160, 180, or 195* deg? Why would I choose one over the other?

If I recall correctly, removing the t'stat housing and pushing the upper hose out of the way helped to get access to the ECT... Even better would be to remove the engine bracket holding the dog-bone in that area... But I was able to replace the ECT by just first removing the t'stat housing and pushing the hose out of the way... I have a swivel head ratcheting wrench that was able to manuver down and onto the ECT... I think it's a 3/4" size... I didn't drain any coolant... When I removed the ECT a few cups of coolant came out... If you are quick you can start threading the new one on before hardly any coolant comes out... I had a 180 t'stat that got stuck open... So I'm back to a 195 right now... Come the summer time I might go back to a 180 t'stat... Also make sure you clear the DTC codes after you do this...

195 will be just keen for ya.

I'll be able to do a more thorough inspection of the whole deal when it stops raining around here, but the info is invaluable Gems. :)

I'm considering a lower temp thermostat because I know the default is a 195deg. emissions-standard t-stat -- this helps the engine reach operating (closed loop, O2 sensor driven) temp quickly so that the wonderful OBDII black box software can make the impala "clean" emissions wise, but on the other hand, all 2001 OBDII equipped vehicles are exempt from (tailpipe) emissions testing where I live (NYC), so I was considering giving the ol 3.8L a break by going to a cooler t-stat -- yep, I'm afraid that the overly modification sensitive big brother OBDII, or even the design of the hard engine may not "appreciate" or respond to the break, so I'm wondering if anyone has been successful in tweaking the tuning this way, and if there is any benefit at all to changing from the default 195deg.?

Gems: I'm also interested in what engine issues (problems?) occurred when the t-stat stuck open -- did the car run better? and/or did it throw codes and tuck it's tail in "limp home" mode?

I didn't notice any difference in engine performance when the t'stat was stuck open... I was still winter when this happened... All I noticed was the temp. gauge was stuck on the bottom while I was driving... The bad ECT threw a code (I think it was P0128) and caused the fans to run continuously... So not only was the t'stat stuck open, but the fans were running constantly... Made for a nice cold engine, especially in the middle of the winter...