P0128 Explained - Coolant Thermostat Temperature Below Regulating Temperature (Simple Fix)

The FIXD wireless OBD2 scanner and free app for iPhone and Android translates your check engine light into plain English so you can rest easy. In this video, we explain what OBD2 code P0128 means and possible causes.
P0128 means an issue with your car's coolant thermostat temperature being below the regulating temperature. The engine control module (ECM) tracks how long it takes for the engine of a vehicle to reach and maintain the correct operating temperature.
When the correct engine operating temperature is reached, the powertrain control module orders the fuel system to enter a “closed-loop” where readings from the oxygen sensors are used to maintain the efficient air to fuel ratio of 14.7:1. Most ECMs mandate that the engine coolant temperature sensor record temperatures above 160º F within 15 minutes of the engine starting.
Additionally, once the 160º F threshold is achieved, the recorded engine temperature must not fall below 160º F during operation. The PCM will record if either of these two criteria is not met. If either fault is recorded again on the next engine startup, code P0128 is triggered.

0:00 P0128 - Coolant Thermostat Temperature Below Regulating Temperature
0:09 P0128 is caused when your vehicle's engine is not reaching the required temperature needed for optimal operation
0:25 Why does your engine need to be hot?
0:50 Possible Causes and Symptoms of P0128
1:22 Visit our blog to learn more about P0128
1:27 Happy Driving!

#FIXD #P0128 #checkenginelight

[fprice]

I just started using the fixd gizmo and I absolutely love it! Easy and quick to use. Amazing little thing

[scottmantai]

That was a great video. Explains it clearly and had a few funny jokes in there. Thank you

[tommyworx]

I am getting p0128 on my 07gl450. I noticed radiator fluid dripping on driveway as well. Thanks for the info...best place to buy a thermostat? Will fixing this clear my engine light that’s currently on? Thanks again for the help. I just subscribed...Boom!

[mohammedalhunaity]

Hello, I suffer from a lack of water in the car, and there is no leaking hoses or radiators, does the thermostat do that in case it is damaged, as I notice a sudden drop in the temperature of the car and it did not rise from its normal position to 80C
when Stuck Open Thermostat is to cause to lack of water, the weather is summer ??

[crissotosj]

awesome explanation for those who don't know about cars

[robertmccabe]

That's what i did got that code changed it and need to put more Antifreeze in thank you

[ChrisAhSnap]

Great explanation thank you, made me feel a lot better. Thanks for the video

[jbreezecoleman]

THANKS! MY ISSUE WAS I HAD NO COOLANT AT ALL, FILLED IT UP WITH COOLANT…CLEARED THE CHECK ENGINE LIGHT AND IT HASNT CAME BACK ON…

[flaknastie]

What if the thermostat was replaced 6 months before getting the check engine light and code p0128? Can it be something else?

[ryans]

Okay when I’m driving on colder days it hovers around 77 degrees Celsius. Then it always trips the light. If the cars idle and not moving for say 5 minutes the temperature goes up to the normal range 90 degrees Celsius. I have good heat in the cabin I can put my hand ontop of the engine and not get burned the hoses feel nice and hot so do you think this is faulty temp sensor. It’s strange when moving it dosnt heat up quick enough when parked and idling it dose.

[kimchee]

How many driving days for P0128 to be gone?

[jdjd]

In my case Opel Astra 1.4 Turbo A14NET, P0128 was the only code, Thermostat was faulty indeed, but dash prompt messages ENGINE GOT TOO HOT so car ECU had to shut down the A/C. Once I open the hood, noticed the fan was constantly working on full, which indicates a CRITICAL problem, the water were not extremely hot, it's because of the faulty thermostat resulting in no water circulation. Button line I want to say this error code can be CRITICAL and severely damage the engine.

[robertokristen]

if this engine check light code was not repaired for long time, what will happen ?
i hear loud noise after 20 - 30 min of driving which is increased by pushing on accelerator !!! is it related to unrepaired coolant thermostat ? or something else !
in dodge durango 2012

[Dean-giie]

Mine says high severity? Its a pontaic grand prix whats the problem to fix there ?

[fdamien]

To anyone who’s automotive educated; If a radiator fan is constantly running, wouldn’t a properly working thermostat opening and closing help regulate the temperature to its operating state thus making a running fan not an issue??

Only wondering bcz I keep having this code pop up occasionally.

Looking at date, code came on when engine was at 165F and vehicle was still in a closed loop. Rpm was around 3400 when the code was capture.

Currently pending a thermostat replacement so hopefully that solves my issue.

[lolah]

Got this code today. Going to dealer to see what's up tomorrow.

[MuddieRain]

I have a code p0128. Can I drive far in it?

[pepper]

i’m in florida so i should be fine, that means something else is wrong?

[BruceWillisiscool]

Also if you replaced your OEM thermostat with a race thermostat, that opens at 160 instead of 180 you will get a code. Replaced mine with a mishimoto amd got the code.

[Gwyntomology]

What's it have to do with O2 sensors?