Check engine light on pulled code P0128???
 

hello,

check engine light came on yesterday. all my gauges looked good and car an good. So i stopped and had autozone scan it and it came up with po128.

definition: Coolant temp always low.

possible causes
1. check coolant level
2. thermostat bad
3. engine coolant temp sensor

checked coolant levels everything ok, had my buddy look at it today and he said he think its the sensor, because my heat is working good and the temp gauge isn't showing the car is cold while sitting the gauge is straight up as usually at 200 and when i go down the road it goes down to about 175 180. what's you guy's take on this?

If the coolant level is good and you have no leaks, then you need to check #2 and #3. #2 will usually make your engine hot because it isn't working. #3 will read that it's cold all the time. If you have a Tech 2 or a scan gauge, and the coolant temp sensor is bad, it will always read somewhere around -38*F (which is about the same *C).

You might also have to add a #4 to your list

4. Check wiring from the coolant temp sensor to the PCM.

ok cool i'll get the the sensor today and try to change it. Is it pretty easy to change?

Which motor? Some are a little trickier then others but either shouldn't be too bad

I'm guessing 3.8.....:D

If you can, check out everything on the list before you buy a coolant temp sensor. It's better that you do the checking first otherwise you're throwing money at the car and you're not sure if it really is the problem or not. There are a number of times when the wiring is the problem and that's why I suggested it too.

The coolant temp sensor is really easy to change though on 3800's. The only thing though is you will need to drain/change your coolant to do it. Otherwise, the sensor is right in front of the engine on the LIM on the driver's side of the engine.

Hope you figure it out. These kind of problems can be pretty annoying and get in the way of just enjoying your car :)

Yeah i'm not really that mechanically inclined to be honest and i have no clue as to how to check the wiring out to the sensor. i've already crossed out the coolant levels and the thermostat cause the cars not running hot and my heat is working as normal. so i definately think its the sensor or the wiring. i pass on what you said to my mechanic and see if he'll be able to check the wiring prior to changing the sensor.

as far as checking the wiring what do you just find the sensor and follow the wiring from it and look for damage to it?

thanks

I found the sensor, the wiring looks fine no cut tares or anything. so im guessing my best bet is to drain all the coolant change the sensor and add new coolant and see what happens.

ok, the light came back on today and pulled the same code. my mechanic changed the sensor last week and put in new coolant. the check engine light had cut off prior to him changing the sensor, and was off for 5 days it came back on today. when i told him he said he know its not the sensor or the thermostat and what he would do is unhook the battery terminal to reset it because he thinks nothing is wrong with it. i guess once i do that all that could be wrong with it is the wiring. it looks good to me.

Whelp i tried the battery thing, it did nothing. Do you all thing it is the wiring even though it looks fine?