Thread: P0128 code

Got the code P0128 - replaced the thermostat and the sensor.. Engine light came back on again, went and had checked again and it read the same code.. Had the light reset- Light came on again about 3 days ago and had it read again and same code and driving home last night and light went off on it own.

Any thoughts?

What temp thermostat are you running?

if you are putting in a colder than stock thermostat you might need some tuning to adjust.

thank you for the replies.. I will have someone look into the wiring and ask about the tuning.. I have no clue on auto stuff, just frustrated with the car and this dumb code.. It never runs hot..

Where would someone check the wiring and how would you adjust the tuning?

if you put an oem thermostat in don't worry about the tuning. I'm not sure what wires you would check

There's an extension harness that goes to the temp sensor that gets destroyed by heat...that'd be your first place to look if you have a stock thermostat in it.

Originally Posted by Slick2500

To add to what Sven said that wire comes off the front of the engine to the drivers side of the oil fill and goes under the dog bone bracket down to the engine temp sensor kinda in a triangle from the throttle body and thermostat housing. Gm put too much slack in this line and it seems to almost always land on the crossover and get melted. There is also the rare occasion where you get a new tstat and it is bad. I have had this happen to me a few times.

Thanks for clarifying Slick...I'm way too lazy to type all that. LOL

Thanks again for the help.... I will see if I can get someone to check everything for me again..

whats the post ?

Originally Posted by squirt

whats the post ?

He was talking about things from the book of face.

ok thanks..

If it is the same code I got twice it's "engine not reaching normal temp in time" I replaced my thermostat with a failsafe then a year later it did it again and I replaced it with a duralast thermostat. Good luck!

New 195* tstat corrected this reoccurring p0128 code that has plagued my instrument cluster since the temperature dropped under 50* air temp.

I also noticed the temp gauge quit touching the 200* mark... Now it sits almost steady right on it. Runs smoother and no more CEL :thumbup:

Sent from Browns country

Thank you for all the good information.. Know to get someone to check out for me..