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Code p0128 on my 2001 kia sportage (is it really the thermostat?)

hello my car has almost 80,000 miles on it and it is the 4 cyl 4x4. the light came on today and i looked it up and it said the engine’s PCM detected that the engine has not reached the required temperature level within a specified amount of time after starting the engine. The intent of the P0128 code is to indicate a faulty thermostat.

so does this mean that the thermostat is failing? ive been questing it lately anyway due to the fact that on the first start up of the day the gauge goes from cold to normal operating temp in under 3 minutes/ around an 8th of a mile i think.

id appreciate any all help

It could be several things.


thats precisely where i went im just tryin to figure out a good starting point i looked under the hood when i got home and follow the top radiator hose and to my delight it stops right under the air duct

This is where the fun part comes in.

Are you a DIYer, or not?

Be honest.

The intent of the P0128 code is to indicate a faulty thermostat. I don’t know what the intent is, but I strongly suspect it is just reporting that for some reason it is getting an indication of low engine temperature. That could be a faulty thermostat or a faulty thermometer.

My advice is to be careful with all those codes. Get the actual code (congratulations you did that right) but don’t jump to a conclusion.

Most all codes indicate a possible problem. However remember that the system that detects the problem may be in error or it is getting a false reading for some reason.

I see mcparadise has you on the right track.

i am a DIYer definately. i like to do just about anything that i can do long as it doesnt involve removing heads.

You’re overdue for a change of thermostat and coolant, IMO, so you might as well see if that fixes it.

I recommend changing “long life” coolant every 5yrs/50,000miles. Regular green coolant every 2 years (and then the thermostat every 4 years).

ok so more than likely thermostat is going and so i need to replace it also should i flush the coolant system or just drain and refil the radiator?

If the coolant looks clean I would just drain and refill.

looked at it this morning to make sure radiator was full as it looked pretty clean

I constantly get that on my Kia. I just keep clearing the code. Mainly cause nothing is wrong. It may be a precurser to the future but I went thru 3 thermostats in 1 year and it turns out there is a software glitch that Kia cannot fix. This came from the dealership. I have an OBDII and if it has that code, I clear it out. If it comes back on multiple times in the month, you may need some further investigation.