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Code P0128

I have a 2003 CE model with just 170, 681 miles on it. I changed the radiator, thermostat, & temperature sensor at 169,556 miles after I had over heated it. I got a check engine light that’s giving me code P0128. The thermostat and sensor are new so I don’t know how it could be failing. The only thing I can think of is that I burned the head gasket when it over heated and it’s causing combustion to either make the temperature sensor get a bad reading or damage the thermostat. The problem with that though is that I’m not getting white smoke out of the tail pipe and I’m not getting milky oil. When I turn on the engine with the the radiator cap off I do get bubbles sometimes though. It seems weird that a new thermostat and or a temperature sensor would already start failing. I suspect it’s the head gasket. What do you think?

You may have air in the cooling system. If the sensor isn’t immersed in coolant, it won’t read properly. It sometimes helps to point the front of the car uphill while filling it.

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I get that you replaced all those parts . . .

But is the engine coolant quickly getting up to proper operating temperature

Just because the parts were replaced, doesn’t mean they’re working properly

I suggest you hook up a scanner and report what reading it displays for the coolant temperature sensor, after driving the car for a few miles

Is the connector for the sensor in decent shape?

How about the wires . . . ?

Good shape?

Or are they brittle, maybe not making proper contact?

High resistance due to bad wiring will definitely affect the temperature reading that the pcm receives

It was rust in the cooling system. I only got that code once and it the temperature gage has always been in the middle. I did a flush and never got the code again.

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