Hello everyone. The other day my CEL came on and had the code P0128 which I am familiar with from about 2 or 3 years ago when I replaced my thermostat with an AC delco thermostat. When the light came on my coolant temperature wasn't reading above 180 F I don't believe. I'm sitting at idle right now after some driving and my coolant reads 189 F and the outside temperate is 36 F.
Does it sound like I need to replace my thermostat again?
I forgot to mention that my coolant level in the expansion tank is above the cold fill line and I don't have any driveability issues. 2005 Cobalt 2.2L base automatic
My guess is that replacing the thermostat would probably clear up the issue. I'm a little surprised that yours is going out so frequently since I've never replaced mine and it's been going strong for ~6 years. How many miles have you racked up?
That code means your engine didn't reach operating temperature in the pre-set delay. This means your thermostat isn't closing tight or the rubber seal has failed.
They replaced the thermostat and a gallon of coolant. According to them the previous person who replaced the thermostat put it in backwards. Very interesting.
Now tht is a new 1 for me. Never heard of tht before. Lol. Thts sad if true
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