Scan code P0128

yes replace the thermostat

Thanks for all your advises. Is there anything to do with radiator or cooling system ? Please educate me how thermostat coolant and coolant temp sensor work.

that code will set when the pcm thinks its taking to long for the car to reach operating temperature, meaning a stuck open thermostat. the sensor tells the computer what the temperature is.

What the high temperature shows on the dash board when car up hill is false, right?

you had access to a scanner to get the code. use the scanner to read the coolant temp. if the gauge goes up and so does the reading then its working correctly

The temp gauge goes up only driving steep up hill. Other than that, the gauge shows normal. It means the gauge is working fine. The thermostat coolant is used to measure the temperature or control or regulate the temperature of the coolant system. if it is used to measure the temperature of the coolant, then it is still good. But it is used to control or regulate the temperature, then it is not good any more. That is what I need to clarify. Thanks for the experts

the thermostat does not measure the temp. its used to control temp. I think the sensor and gauge are fine. Ive replaced many thermostats on behalf of that code. and it has always fixed the code.

Thanks a lot for your information

I finally changed the thermostat and took care of the problem. Thanks a lot for your information

My wife drives the 1999 Lexus RX 300. The check engine light came on recently. We diagnosed with code P0171 for too lean bank 1. We did clean the MAF sensor but the problem is still there. We also smell too much gas. I believe it does burn all gas. However, the engine run strong and smooth. No rough idle or crap. I don't know what to do next. Any of your advices are very much appreciated.

I mean it does not burn all gas.

My wife drives the 1999 Lexus RX 300. The check engine light came on recently. We diagnosed with code P0171 for too lean bank 1. We did clean the MAF sensor but the problem is still there. We also smell too much gas. I believe it does not burn all gas. However, the engine run strong and smooth. No rough idle or crap. I don't know what to do next. Any of your advices are very much appreciated. Thanks

Water temp switch Replace not efi