Code PO128 Coolant Thermostat Performance

Supermoto68

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Jan 17, 2021
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I keep having this code pop up over and over, does it have to do with my tuner ? Any help would be appreciated
 

2004LB7

Well-known member
Dec 15, 2010
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Does your engine seem to be running cool or taking a while to come up to temp?

More then likely it is bad thermostats or temp sensor
 

ikeG

Oughta Know Better
Apr 19, 2011
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If you Google it, people have copy pasted the diagnostic instructions into a reply on other forums.
If you find the thermostats are good and ect sensor is accurate, you end up testing circuits. Any resistance will make the sensor report a lower temp than actual, which the ecm sets p0128 for.

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Supermoto68

New member
Jan 17, 2021
26
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1
Does your engine seem to be running cool or taking a while to come up to temp?

More then likely it is bad thermostats or temp sensor

I have been watching my temp in my truck an it seems to be running around 185 degrees all the time. Is this below normal as my truck keeps setting off this sensor every few days.