IF you replace the ECTS, be sure to get one from a Saturn friendly GM dealership along with the pigtail. Make sure it's brass tipped too. The crap you'll get from the zone, advance or other chain stores won't be properly calibrated.

 

Went to town early when temp. was 21 deg.(pdc for here) and the danged light didn't come on. I warmed the car up in the driveway and closely monitored engine temp. In under 2 minutes the temp. came up to the minimum mark and was on the rise. Over the years I've noticed the heater starts having an impact about the same point out of here (around a mile) and it definitely did that. So.....if it's a thermostat problem it's definitely intermittent.??? (I'm asking)

At this point I'm not going to plan on changing out the thermostat due to amount of junk to remove to get to it. I'll wait until I see something that convinces me it's the thermostat. Is this a good or bad approach?

I will probably go ahead and swap ECTS's ......maybe after I get the light on one more time. Again, good or bad approach?

The only thing I've determined for sure is that it's not a good idea to tell your wife to put a little dab of duct tape over the alarm light.

 

Also make sure coolant is full the cap holds posted pressure. Make sure you have no leaks including the water pump, coolant cap. Check plastic radiator tank is not leaking on the drivers side facing the rear of the car. Look for swelling or cracking of the plastic tank.

 

Looks like I got this code P0128 on my car yesterday, along with service engine soon light. I have been suspecting that it is running colder than it is supposed to. Temp on scan gauge shows it around 145 to 150 most of the time. I have the new thermostat, just not had time to put it in. Fan has been running all the time also the last 2 days.


derf, found a previous Auto Zone printout for this condition and the code is P0128 Engine coolant temperature below thermostat-regulated temperature.

 

indeed, but this is an L series post and you drive an SL1.
The thermostats on the L series V6's required tons of disassembly to get to for replacement....not so for the S series.