Just joined the site, so thanks in advance for any help. Also just bought my first 2004 Mazda3 and love it so far. Quick, responsive and fun to drive. But as I was driving to work the other day, the orange engine light came on. I had it hooked up to a computer and it read PO128 - coolant thermostat problem. The Tech said that the coolant wasn't getting hot enough fast enough. They checked some stuff and said everything looked ok, reset the code, and off I went. 4 days later the light is back on. I'm thinking it's time for a new thermostat, the original one is still in there. I hear that it isn't an easy job, as you have to replace the whole housing around the thermostat also. Any ideas about that code, what I may be looking at or if anyone has dealt with this before? Could it just be a faulty sensor, or is it time to replace the thermostat (and hoses) anyway?

 

after changing Tstat I would advice you to go to dealer and check if your pcm has the latest update. I belive there was a PCM update for that code.Tstat ussually takes about an hour to do, 3olts and 2 hoses

 

Thanks for the info. I have the thermostat being replaced along with the two radiator hoses today, since they are all original parts. And even if that isn't the problem, they need to be done anyway. Next step is getting the car to the Mazda dealer for a computer update as you suggested. I'm sure it needs to be done anyway.

I appreciate the help.