Hello all. New here, I have an '03 Trailblazer 91,000 miles, myservice engine light was coming on after every gas fill up then would go off once I hit a half tank, so I switched gas stations and after a couple fill ups I went and bought a new gas cap. Went to today to auto zone because it still came on and the code PO128 which gave 3 options, coolent was low, thermostat sensor was going out, or thermostat was going out. They checked my coolant and it is full and looks good. Is this something I should just go ahead and take in the dealership? and is this going to be an expensive bill? ..lol Thanks in advance!

Christie

 

I am having the same problem. Did you get yours corrected and if so, was it expensive? Thanks.

 

P-0128 is usually a thermostat that has failed-- or beginning to get lazy.
the good thing about these thermostats is that they fail in the OPEN position.
so very rarely will you see an overheated trailblazer...
usually the engine begins to run cooler than normal- and the computer detects this- and sets the P0218 code.

the fix is to replace the thermostat.
Price wise-- Im guessing at least $500 at the dealer...
The part is about $30.
and 2 bottles of premixed dexcool (wal mart has them) about $12.
You can replace the thermostat yourself in about 3 hrs with directions.
I did a HOW TO on another website.