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check engine light on my 04, I got the code 0128

2104 Views 17 Replies 4 Participants Last post by  meyer3201
Just came on a couple days ago, gave me the code 0128 Coolant Temp Below Thermostat Regulating Temperature.

Anyone else ever have this problem? Is it save to drive?

Thanks for your help!

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Re: check engine light on my 03, I got the code 0128

03? you mean 04?

I got that same thing on my '04 before I traded it in. Dealer said I needed a new thermostat and quoted me $330 to replace it. I had 0126 and 0128 codes. Do you notice that it takes a long time for your car to warm up? Thats a pretty tell tale sign that its the thermostat. Its perfectly safe to drive.. but you may want to get it fixed.
Re: check engine light on my 03, I got the code 0128

oops, ya I mean

That was my first assumption, why so much to fix though? I gotta go see where this thing is located. Sounds pricey for a thermostat.

Thanks for the reply, I haven't noticed it taking longer to warm up or any warm up issues. The guage did seem a little higher than normal. I think it usually sits 1/4 the way up but right now it's sitting in the middle.

Hmm.. mine always sits in the middle between hot/cold. Always did on my 04, and does on my new 09. I also have no idea why that particular dealer quoted me so much. The thermostat itself is only about $40. Theres a how-to on here for replacing it... its on the backside of the engine (firewall side) if I remember correctly.
maybe that's why it's so much then. might not be easy to change.
Yeah, it might not be easy to change. Just take it to your dealer and tell them to check it out. They'll probably pull the code themselves just to make sure. I dont know how many miles you have, but I hope you're still under warranty ;).
It ran out all ready. :( I just took it in for service and they wanted like $50 to just put in on a scope. Freakin BS if you ask my. I have a ob2 reader and got it in 10 seconds. I told them If I couldn't fix it myself I will bring it back too them and I won't have to pay for the scope if I have the code.
I am going to disconect the batt and see if it comes back.
It'll come back.. just not right away. Generally they wont do the service unless they actually read the code. You're lucky if they only charge you $50 to read the code.. the dealers around me charge $100.
ya, most places I know charge that too. I was suprised but knew I could do it for free. I was also suprised when they said I could give them the code to use for there reference
Hmm, maybe your dealer will actually believe you and not have to pull the code. One of the dealers I go to said they had to pull it themselves.. but I think thats just their way of grabbing more money out of their customers pockets.
i agree but if I was working on the car I would want to pull it myself, just so your not working on somthing that has nothing to do with the problem and you waste all your time on someone elses diagnostic.
I unplugged it and it has beeen gone for days now. Guess it was nothing. Good thing i didn't waste my money at the dealership.
And thanks for all your advice sdemo45, Seems like you where the only one that would help out.
No problem... I hope it doesnt come back on you. Good luck ;).
pavich...just noticed this thread. Do you have atx or mtx? If you put PO128 into search engine (use capitals for PO) you'll find a few discussions on this CEL which only a few of us had back in '04, '05, '06. Happened mainly to '04 2.3 ATX owners. Had nothing to do with thermostat. I had my computer updated in feb '06 and both my gas mileage and heater improved. The problem was the coolant temperature sensor was reading the coolant as cold when it was actually warm. The update fixed it. Are you getting lousy mpg and poor performance from your heater?
WOW, another reply, I was beggining to think this site didn't help

Thanks for the reply. It is an auto and 04. Heat still pupmps nicely but I have noticed the milage getting worse. So you say I just need to go in and get my computer updated? Does that cost an arm and a leg?
You likely didn't get many replies because only a few of us, who live in areas with very cold winters, had the issue. My update was done under warrantee. So I don't know what Mazda may or may not charge.

Are you the original owner. If not, check around the hinge of the driver side front door. If you see a sticker there your car probably had the update done before you bought.

Here are all the TSB's for the 3....
Just scroll down to the one that mentions PO128 and click for information on this TSB.

If your check engine light hasn't come back on I don't know that I'd be rushing off to mazda to get the update done. Just monitor your mpg #'s.

I did say in previous post my mpg improved but it wasn't significant. What really improved was my heater performance. Prior to update it worked so poorly I was ready to trade it off as in -40* temps you do need a heater that works.

Good luck.
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I guess I'll just leave it for now and hope it doesnt come back. my heater works pretty good.
anybody know what this update cost, i have an 04 with 70k m/t ive thrown this code twice???
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