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Ron, ASE Certified Technician
Category: Hyundai
Satisfied Customers: 33065
Experience:  35 year in the Auto repiar business ASE Certified
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Being dealing with a 3month problem on this 2008 accent. All

Customer Question

Being dealing with a 3month problem on this 2008 accent. All started with a broken timing belt that lead to me rebuilding the head with new valves, all new sensors (since all the parts where cheap, I got the coolant temp sensor, osv, cam and crank), water pump, timing belt, drive belt, tensioners and a few other misc items....basically rebuild the whole top of the motor...
during the repair I didn't disconnect the computer which is on the drive side, I just moved it to the side of the car out of my way, but obviously that would have moved the main harness around some.....
Car runs awesome but I cant keep P0128 and P0128 pending from coming on....I had reused the t-state, so I then switched to a new OEM that opens at 180 F (there is no hotter t-state for this car). After doing this, the CEL stayed off for 154 miles, before it was going on at 40 miles, so the new t-state definitely helps. My theory is that the new water pump is of a better designed then OEM and pushing coolant past the new t-state AND/OR the new coolant temp sensor is bad or a connection is loose.
At the moment I only have a basic scanner but I am getting one today that reads live data such at coolant temperature, however if that sensor is bad, will this throw off the live data information?. Some other questions:
1. If I can see the temperature the sensor is reading via live data, will this help to figure out the problem. What if the temp sensor is sending wrong voltage to ECU?
2. What else can I do and what other data do I need to get from ECU/live data readout? Is it easier to maybe just replace (again!) the coolant temp sensor, it is hard to get to, that is why I changed it when I had the head out of the car.
3.. If I take a good automotive shop, will this probably be a basic disgonisic fee or will they want to charge by the hour? Seeing they would have the better scan tool and more experience, I am hoping it is just 90 dollars (that is the standard here in california)
I am trying to fix this myself, so please respond in light of this, thanks. I have had three experience experts on here help me on this but at the end of the day, the problem is not fixed, so looking for someone that has hopefully dealt with this before.
Submitted: 6 months ago.
Category: Hyundai
Expert:  Ron replied 6 months ago.
Hello, my name is ***** ***** I am a professional here at Just Answer. I have noticed that your question was not getting a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.The code P0128 indicates the engine coolant signal is below manufacturer specified temperature and in most cases this code set due to a failing thermostat or you have trapped air in the cooling system. If you are sure both are okay then I would run the pinpoint test for this code. I have enclosed in in the link below. Copy and paste the link to your browser to open and view it.
Customer: replied 6 months ago.
I have already done most of what is suggested, if you see in my question I have addressed most of this.....everything pretty much is new, including the OEM T-state....
I think I need to know how to check the connection from ecu to coolant sensor?
Please re read my orginal question and advise, thank you
Expert:  Ron replied 6 months ago.
Okay, see the wiring diagram in the link below for checking the harness from the ECT to the ECU.

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