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02 Sonoma service engine soon lite


02gmcsonoma
12-08-2005, 02:35 PM
Code PO128 kept coming up.Changed thermostat and will see what happens.Any other repair suggestions for this code??

gmc2003ZR2
12-16-2005, 10:40 AM
P0128 - Coolant Thermostat (Coolant Temp Below Thermostat Regulating Temperature)
I just added coolant to my zr2 and the temp is runing around 160+- when it usually runs @ 240+-.
Is it safe to drive if coolant resivior is full?
How do you clear this code?
Do I need a new Tstat?
Does it need to be cleared by a shop computer?
Is it hard to change, if you are mechaniacally inclined)
any help is much appreciated!
:eek7:
Matt

GMMerlin
12-17-2005, 02:09 PM
P0128 - Coolant Thermostat (Coolant Temp Below Thermostat Regulating Temperature)
I just added coolant to my zr2 and the temp is runing around 160+- when it usually runs @ 240+-.
If you added coolant, check for a leak
Is it safe to drive if coolant resivior is full?
YES, but see answer above
How do you clear this code?
You need a bi-directional scanner....you can try disconnecting the battery, but that doesn't always work
Do I need a new Tstat?
Possibly, but I would check for leaks first
Does it need to be cleared by a shop computer?
Answered that one already
Is it hard to change, if you are mechaniacally inclined)
No
any help is much appreciated!
You are welcome

serpentracer
01-01-2006, 06:31 PM
first of all your temp is normal at 160
240 is not
you can also clear codes by pulling the ecu fuse.
my truck had this code before I cleared it and it has not came back on. I have a scanner and it clears codes. I have not tried the fuse deal.
if your temp is running at 240 you probably need a new thermostat. and make sure you have sufficiant coolant levels in the radiator and overflow tank.

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