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383 Posts
Discussion Starter #1
HEy all, my check engine light turned on so i called ONSTAR and did the diagnosis. They said that my car gave back 2 codes:

P0128 - Coolant Thermostat Below Thermostat Regulating Temperature
P0446 - Evaporative emissions.

They also mentioned that i might or might not lose engine performance with one of these codes i cant remmember.

Well i cant get my car serviced until sometime next week. The light came on 4 days ago. Do you guys think it would be safe to keep driving it for that long?

Is this really serious, can it damage some other part of my car or any chance my car would stop?

Thanks alot for your help
 

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The Mighty Kael, 2004 Black CTS, Every Option
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if its real bad liker service "right now!" usually they will flash, the manual has a way of how to check for codes through the nav as well


i think you might have low coolant or the radiator cap is loose or gas cap is loose.
after that its a leak in the system somewhere.
i have seen these codes for that before on obdII cars.
P0128 ECT Below Thermostat Regulating Temperature(GM)
 

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1994 Fleetwood 60" Stretch; '07 Avalanche, '95 Nighthawk
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3,963 Posts
The 446 could just be a loose gas cap. Make sure it's tight. The code is telling you that the engine can't pull a vacuum on the gas tank because there is a leak somewhere.

The 128 is tougher. It could be the thermostat itself or the temperature sending unit.

Jim
 

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Cadillac Technician
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Probably a sticking thermostat or low coolant and a loose gas cap, possibly a vent valve problem in the EVAP system.
No big deal but you may not have much heat in your car.
 

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Discussion Starter #7
what i hate about it is that you cant tell how much my engine is heating. 2003 CTS has no engine temprature gauge
that SUCKS!!!!
 

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I noticed your post back on the P0128 code..can you tell me where the temp sensor is located? I have this code set and cannot get it to reset with a scan tool...the engine runs fine and has plenty of coolant, so it must be the sensor..if the thermostat was stuck open the car would never heat up and since I am in the middle of winter here in VA, I would know that...appreciate any help here...thanks
 
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