2008 trailblazer p0128 code

Question

i have a 2008 trailblazer, after clearing the code p0128 the temp gauge works and ac works, after i driver for 20 miles the temp gauge will read 100 and the ac stops working then the cheek engine light comes on, i clear the code temp gauge works again and ac works again. i have replaced the ECT sensor. still the same thing. i beleave its a computer problem im having but not totally sure and if it is im not sure if i should get the PCM or the BCM reprogrammed

Answer 1

BCM this is for Body control module, such as window and you a/c controls. P0128 is thermostat below regulating temperature even with this code the a/c system would still work. and if the scan data say 100 for the temperature the a/c would still work. because the ECM set the code the problem is a powertrain problem with the ECM, If the BCM set the code then its a BCM problem. The only time the a/c temperature would go off is if you disconnect the temperature sensor then the scan tool temperature would read -40. the transmission would also exhibit a bump at times when it shift gears. then the a/c would not turn on. also if it reads a overheating problem Depending on the engine size the coolant temperature sensor has a 5 volt reference that is shared with the MAP sensor , throttle position sensor , there is no way this can be a ECM problem. you would have a variety of codes.  replace the thermostat and check the coolant level, or if use just water. make sure the radiator full, and get a safety pin and bring up the connection of the coolant temperature sensor so it makes proper contact.

Comments

100% correct i changed the thermostat today and sofar i have drove 45 miles and everything is working great. i was just so sure it was a computer problem couse i been reading alot of forms with having the same symptoms even after replacing the thermostat and ect.......................thank you very much for writing