lucerne 3.8 code p0128

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check engine light came on, code reader says it's a p0128 coolant temp too low...anyways, the car seems to warm up fine , and I get hot air from the heater, however the temp gauge when driving is about 1/8 inch below the normal mark whne the car is fully warmed up...what do you guys think?
 
Have you monitored the coolant temp via a scan tool?

Check the current coolant temp against the specified coolant temperature in the factory service manual, and also follow the troubleshooting procedure for that DTC in the service manual.
 
Originally Posted By: lucerne06
check engine light came on, code reader says it's a p0128 coolant temp too low...anyways, the car seems to warm up fine , and I get hot air from the heater, however the temp gauge when driving is about 1/8 inch below the normal mark whne the car is fully warmed up...what do you guys think?


I just went through the exact situation with a 97 3.1 chevy ,It was the ( coolant temperature sensor ) If it warms up fine and has heat it is not the thermostat but since the sensor is usually near the thermostat change them both
 
thanks, also how do I tell if my t stat is a 195 or a 180?? it's a 2006lucerne 3.8, and it lists two t-stats for it...
 
You stated your vehicle runs colder than normal your thermostat is stuck open. Check your thermostat first then progress to next step. Been there done that.
 
Originally Posted By: lucerne06
thanks, also how do I tell if my t stat is a 195 or a 180?? it's a 2006lucerne 3.8, and it lists two t-stats for it...


A thermostat is one of the few items that I always get from a dealer.

And you'll want a 195 for that engine.
 
Your welcome,,,I looked on my old and new one and did not see any identification ,,Regardless if your in the upper USA your going to want to get a new 195 ,,southern states a 180
 
Dont deviate from the OEM temp...computer operation and emission control depends on a warmup within a certain timeframe.A low temp unit will possibly stretch it out and kill mileage even more.
 
I had that code come up last month when it got really cold. I erased/reset the code and it hasn't come back on since, I would try this first before replacing stuff.
 
Pulling the negative battery terminal or clearing codes with a reader is hoping your cars computer was wrong, that a computer made a mistake. Its ignoring problems, living on borrowed time and risking a potential bigger issue down the road. Leave the CEL on for now, don't play code clearing games with cooling related CEL's.

Whats up with the coolant? What are you running and when was it last changed? I would change/drain and fill it along with the thermostat. Old coolant can cause thermostat problems. May be a good time to abandon Dex Cool if thats what it is. Use Peak Global Lifetime.
 
Yes, you need to replace your thermostat. I've addressed several P0128 codes with thermostat replacement. Easy job except for a CTS where the thermostat is BEHIND the engine buried.
 
Going to attempt to replace the termostat myself, never did one before...seems pretty straightforward,,,any suggestions?/

also Do I need to drain some coolant out first?

ended up getting a stant superstat #45849 and a felpro gasket.
 
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