Problem with  my 2003 Pontiac Grand Prix
V-6
Check Engine Soon
codes = p0128
Repairs done prior = Recently had engine cooling system flushed and coolant
replaced  

tech = JK
question = Just as my car turned over on 170,000. Why does my check engine light
came on. I had Auto Zone check code. Came up p0128. Light stayed on
for about 50 miles then went off. Any ideas as to what this might be...or
should I just leave it alone until it comes on again?

Thanks a bunch...


JK:
Thank you for the tip/donation.

This code is described as 'coolant temp. below thermostat regulating temp or threshold'
A common cause for this code is a sticking thermostat. The coolant temp is too low for
longer than the pcm(computer) expects. It is possible that there was an air pocket in the
system after the flush and that caused the code. Keep an eye out for the light to come
back on, coolant temp gauge (if you have one) to stay low, poor heat from heater/ac
system, or colant fans under the hood stay on with car off. If some of these things
occur, then have your thermostat changed, and make sure the system is bled of air
after re-filling the coolant.
Pontiac Grand Prix OBDII code P0128 coolant temperature.