p0128- 2004 chev malibu

[Mike M 4]

Ok, I know this is not a chev site, but I have not found one worth while. P0128 code, looks like the ECM dosnt think the car is operating at the right temp. I reset the code last night to see what will happen. CEL came on initially right after a cold start up. Car gets up to temp. How do you test the temp sensor? OBTW, he dashboard temp indicator is working that is why I reset the code.



Mike

 

[EddieS'04]

It will have a resistance in ohms from a base temp to a max temp. you would have to have a gm manual for the info. They dont cost much. It will be a different sensor than the one for the gauge.

 

[Torrie McPhail]

My guess T stat :



Thermostat Rationality:

A method is provided for testing a thermostat in a motor vehicle. The method includes an engine warm-up model and a thermostat diagnostic. The engine warm-up model predicts the temperature that the engine coolant temperature should be equal to at a given time after start-up. This is based on the engine coolant temperature at start-up, ambient air temperature, and how the vehicle is driven subsequent to start-up. This predicted engine coolant temperature is compared to the actual engine coolant temperature as read by an engine coolant temperature sensor. The error between the predicted engine coolant temperature and the actual engine coolant temperature is calculated and integrated over time. The thermostat diagnostic runs at a pre-selected temperature after start-up and compares the integrated error to a predetermined threshold value. Depending upon the results of the comparison, a pass, fail, or inconclusive condition is determined.





Take care,

Mr. Torrie R. McPhail - (Owner)

http://www.FastPartsNetwork.com

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[EddieS'04]

Could be T-stat. But if the cel came on right at startup, I think sensor..

 

[Tom Schindler]

Another thought.



I do not know much about GM's, but on other vehicles...including one GM, I have seen two temp sensors. One for the guage on the dash and the other for the ECU.



This was true with my brother's 1990 C3500 with a 454 V8. The engine would idle at 3,000 RPM. The ECU said the ECT Sensor was reading too low. Aparently, the sensor was telling the ECU the engine was very cold. The guage on the dash said the temperature was normal.



Swapped out the sensor and the engine ran perfect.



Just a thought. Don't know enough about GM's engine managment to comment any further.





Tom