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P0128 CEL, Temp seems Normal

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Old Aug 2, 2017 | 12:54 PM
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2015 C400 Tenorite Gray
P0128 CEL, Temp seems Normal

I got the P0128 code. I was running low on coolant and topped off. Problem is the CEL is still on which seems weird when operating temp is 85.

Is this a sensor issue? P0128 code
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Old Aug 2, 2017 | 03:03 PM
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Tried to clear with an innova but it would not work. It shows the code 3 times: freeze frame, pernament, pending.
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Old Aug 10, 2017 | 02:00 PM
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Had that code several months ago. Bad thermostat.
For my case, I couldn't clear the error from memory, as it's pending I suppose. The light will go away but the error couldn't be cleared with my code reader. The light will come back after awhile.

Engine temps looked normal to me too. But I guess it was because the engine took longer than usual to get up to normal temps. Not sure what the specified time is, but that was the problem. I replaced the thermostat and I didn't notice a difference in engine temp, but the code went away completely lol maybe it was off a few degrees but unnoticeable from the gauge.
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Old Aug 10, 2017 | 06:29 PM
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Thanks for the comment. there's no heat in the car and it comes on rarely only when driving.

I presume that there's no danger putting this off?



Originally Posted by 95Sinned420
Had that code several months ago. Bad thermostat.
For my case, I couldn't clear the error from memory, as it's pending I suppose. The light will go away but the error couldn't be cleared with my code reader. The light will come back after awhile.

Engine temps looked normal to me too. But I guess it was because the engine took longer than usual to get up to normal temps. Not sure what the specified time is, but that was the problem. I replaced the thermostat and I didn't notice a difference in engine temp, but the code went away completely lol maybe it was off a few degrees but unnoticeable from the gauge.
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Old Aug 10, 2017 | 06:42 PM
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Judging from your engine temperature it's not being a big issue. It's more for emissions purposes it's not good since the car pollutes more when the engine is cold and not running at operating temps. It's not good to run in this condition for long periods of time too, since the engine runs leaner and your fuel economy will be worse. But your case (and mine) doesn't seem to be a stuck open thermostat where the engine is cold for a very long time. So you could probably get away with running like that but pay close attention tho, the thermostat is on its way out. It may be stuck open on you one day or even worse, stuck Closed.
If your have emissions test coming up it will auto fail too with a CEL.
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Old Aug 10, 2017 | 06:48 PM
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Luckily, I just had it smogged before the CEL.

As for fuel economy, it's difficult to tell since I've been running the A/C

But to your point, yeah, I know I'm on borrowed time.

Thanks

Originally Posted by 95Sinned420
Judging from your engine temperature it's not being a big issue. It's more for emissions purposes it's not good since the car pollutes more when the engine is cold and not running at operating temps. It's not good to run in this condition for long periods of time too, since the engine runs leaner and your fuel economy will be worse. But your case (and mine) doesn't seem to be a stuck open thermostat where the engine is cold for a very long time. So you could probably get away with running like that but pay close attention tho, the thermostat is on its way out. It may be stuck open on you one day or even worse, stuck Closed.
If your have emissions test coming up it will auto fail too with a CEL.

Last edited by Nicholi2007; Mar 3, 2018 at 08:03 PM. Reason: damn grammar
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