chevygirl027

I have a 2002 Camaro with 207,000 engine light comes and goes and has for a while. I pull the code and sometimes it is the "emission" codes but today it was the p0128. Most of the time the temp guage works fine, but other times it does not move and the cooling fans come on immediatly when I start it. I figure there might be many things but would a new thermostat sound like it might be the fix in this case. I have read that the fans will come on if the guage is not working. I have read that thermostat is pretty simple but however I am a female and have little knowledge but can do a few things myself with the book. I hate going to shops and have been running with the engine light on and off for months now but its about time for emissions and palte renewal :-)

transamtom

I installed a larger V8 rad and a 180 thermostat and always get this problem.

I keep a code reader with me to clear it.

The reason for the trouble code is GM's dual purpose sending unit,it sends a signal to the PCM and also to the guage.

The problem occurs when the PCM doesn't see a certain temperature in a certain amount of time,it thinks there is an error or fault with the sensor and defaults to the cooling fans on to protect the engine in case of overheating.

Mine happens mostly on sub 40* days while driving on the Freeway.

Changing to a 195* thermostat may help.

mrwoopass

There is a temperature switch / sending unit sensor that reads the coolant temp in the block. This is what operates the needle in your dash. If this sensor is bad the needle will not move and the fans will come on immediately, and give you that code as a protective measure. On the V6 this is located right below the throttle body screwed into the intake manifold. Its kind of right above the engine belt.

If the connector to the sensor is bad, this can happen as well (personal experience). I would try to find the temperature sending unit and push / wiggle the wire a little bit while someone is in the car to see if the needle moves. If you have access to an OBDII reader with live sensor status you can see the reading of the temperature say something along the lines of -35 degrees, and as you move the cable / connector it may flip around to the proper reading. If this happens, I would consider changing the wire. You can get a replacement pigtail at your local auto parts store. Same for the sensor.

If you want to test the sensor, remove it, and put a multimeter to it on the ohm setting and lookup a chart for what ranges you are looking for. I like to put it in the freezer a bit and test it then, and then put it in a pot of hot water and test it that way as well to see if it has a proper range.

Best of luck!