2001 Chev Lumina 3.1 v-6

I need to change the thermostat and wonder if I have to remove the throttle body to do this? I have looked it over according to a repair manual I have and it doesn't mention this. It runs well, however the temp gage only gets to above the second mark on the left side. The heater works fine and no leaks. It has 145000 miles on it. Just returned from 2000 mile trip and gas mileage was low 28mpg and high of 37.3, from Ks to Utah and back. Have never had any problems however my svc eng light is on and code indicated it may be the thermostate. Any advice?

Welcome to AF. If it were running below the normal operating temp you would have set a code, normally, yes the TB must come off.

The throttle body and the exhaust crossover pipe might need to be removed as well for clearance.

You can do it without taking off the TB, but it will take just as long and probably be more frustrating that way.

Ask me how I know, haha.

Thanks for your info. I appreciate it very much. GaryYou can do it without taking off the TB, but it will take just as long and probably be more frustrating that way.

Ask me how I know, haha.

do not believe you will show a code for thermo, sounds like a temp sensor problem

sounds like a temp sensor problem, bad sensor may be telling comp. engine is colder than it is thus it will run rich causing bad mpg

sounds like a temp sensor problem, bad sensor may be telling comp. engine is colder than it is thus it will run rich causing bad mpg

I disagree. Normally when the CEL illuminates and the code stored is P0128 - ECT Below Thermostat Regulating Temperature, it's a stuck t-stat, not the sensor.

I disagree. Normally when the CEL illuminates and the code stored is P0128 - ECT Below Thermostat Regulating Temperature, it's a stuck t-stat, not the sensor.

Second.

I would for sure replace the thermostat with that many miles.
The low temp by itself will not turn on the CHECK ENGINE light.
Change the thermo, flush the system, put in new anti-freeze, check your hoses (tighten clamps), check the radiator cap and look for leaks.
After you have done all of this neccessary PM and your light is still on check the sensor.
Get your hands dirty and let us know what you find.

good luck, grouch