Saturn 2004 ION 3
 

I have a '04 Saturn ION 3 - 119,000 miles, purchased new and meticulously maintained, but recently the radiator 'blew'. I've had all the elements related to the heating/cooling system replaced: Thermostat, water pump, temp sensor, fan belts, coolant, O2 sensor The car runs great, but the temp gauge does stay a bit on the cool side. Prior to all this the temp was always right in the middle. After all the new parts, the engine light came up with a code of P0128. This was after the first 5 parts were replaced, the engine light came on after about 60 miles driven. Then we replaced the 02 sensor but the light came on again at about 80 miles driven. Any advise as to what might be causing the engine light to still come on? Is it possible that a non-factory part might be the cause? Any assistance would be very appreciated:)

And thank you!

Can you please clarify specifically which codes followed which specific part replacements?

It's a bit unclear as expressed above, as you came up with a P0128 (Engine Coolant Temperature Below Thermostat Regulating Temperature) code after replacing the ECTS and the thermostat at the same time.

Not sure why you would throw an O2 sensor code afterwards unless the car is still running in open loop mode which means it is running very rich and may have poisoned the sensor. But you didn't supply the O2 code. What was the code? Or course it could also be time to change as 100K is the average life of a front O2 sensor.

Then you state another code was thrown 20 mi later. Which one?

So is it just P0128 or are there other codes

If it is P0128 only, the most likely causes are a thermostat stuck open or a bad ECTS.

I would lean towards either a bad temp sensor or stuck open thermostat. Me I would test the temp sensor first then move to the thermostat. good luck

Make sure you used the proper temperature thermostat. If you used a 180 instead of a 195 this may be all that is wrong.

On our ION when I got the car it had that code, someone before me must have tried to put one in.

What I found was the rubber o'ring around the thermostat got kinked when they installed it, I bet that is your problem too.

Thank you very much to tooter1, Derf, 02 LW300 and scoffman for your responses! I appreciate it.
I will let you know what was causing the reoccurring engine light as soon as I know:)