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My radiator blew with the transmission fluid mixing over the summer. I did the flushing of the transmission fluid and coolant and thought I made it out alive haha. Now the weather has gotten a Little cooler and the P0128 check engine light popped up on my 2005 mdx. I'm not really notice any temp problems but should I just change the thermostat? Does anyone have photos of the replacement process? I'm thinking I might be able to just do it myself. When I got the code read at advance auto they did it's most likely the thermostat. Thanks for the help!
 

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What does your temperature gauge say? Does your fan come on when the engine is running and the temperature gets over half-way up the temperature gauge? There are quire a few things that can cause the error code, and I don't recommend just throwing parts at the problem since you really don't want to seriously overheat your engine if you guess wrong.
 

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What does your temperature gauge say? Does your fan come on when the engine is running and the temperature gets over half-way up the temperature gauge? There are quire a few things that can cause the error code, and I don't recommend just throwing parts at the problem since you really don't want to seriously overheat your engine if you guess wrong.
The temperature gauge stays below the halfway point. It seems like its a bit slower to warm up which is why I thought the thermostat would be the issue. I haven't noticed any issues with the fan or overheating yet.
 

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One of two things is happening - either the engine is getting hot and being reported correctly by whatever process creates the P0128 code... or, the engine ISN'T getting hot, and whatever process produces the P0128 code went wrong.

I'd still recommend letting the engine idle until it's good and warmed up, and see if the cooling fans come on. If they don't, the engine WILL overheat, especially with the A/C on.
 

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My radiator blew with the transmission fluid mixing over the summer. I did the flushing of the transmission fluid and coolant and thought I made it out alive haha. Now the weather has gotten a Little cooler and the P0128 check engine light popped up on my 2005 mdx. I'm not really notice any temp problems but should I just change the thermostat? Does anyone have photos of the replacement process? I'm thinking I might be able to just do it myself. When I got the code read at advance auto they did it's most likely the thermostat. Thanks for the help!
My 05 had the same issues with the radiator and tranny fluid mixing like 4 years ago. And now i get the same code P0128, so i changed the water temperature sensor a few days ago and the engine light came back on. My engine temp reads normal like it always has. I dont know what to do next. And suggestions???
 

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You guys need to either have the problem diagnosed, or do some of that yourself. The intent of P0128 is to alert the driver to an engine that hasn't come up to operating temperature in a "normal" amount of time. There are a lot of variables and inputs that are considered, including the Engine Coolant Temperature (ECT) sensor, the Intake Air Temperature (IAT) sensor, and the thermostat itself. It's unwise to just throw parts at the problem hoping something will fix it.

For those with the code on right now: what is the ECT sensor reporting to the engine after the engine's been running for a while? What about the IAT sensor? Is it reporting "near" ambient temperature or a little higher? Replacing the thermostat may not be necessary, and there is no single "P0128 sensor" -- a number of inputs come together from a variety of sensors to set this code.

If you would like to diagnose this yourself, I would recommend a code reader that can display real-time sensor data. Or, download "Torque" on an Android device and pair it with an inexpensive Bluetooth OBD-II dongle off Amazon. You'll be able to see exactly what the ECT and IAT sensor are reporting and will be able to make an informed decision.
 

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I just flushed my radiator last week and found my reserve was empty. I read that that was the problem. So i filled my reserve up to the proper level and ill wait until the engine light turns off by itself, hopefully 😀
 

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I'd recommend that anyone with a smartphone and $10 buy a bluetooth OBD "dongle" and get the Torque app on their phone. That will give you the ability to read and reset the error codes your car might be throwing, and will let you monitor lots of vital things like coolant temperature, ignition advance, etc. real-time (at least on the paid version - the freebie version of Torque still lets you do everything you really need to do). Having this super-cheap capability will likely save you hours of thrashing around guessing at problems in the future. The dongles run about $10 delivered from places like amazon.com.
 

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I have OBD reader. I scanned it and dont know what the numbers mean. I wrote down these 2 that were in the negative. STFT. B1 -11.7 and STFT B2 -7.0 i dont know if these are good or not. I only wrote them down because they were the only oned in the negative.
 

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That is your Short Term Fuel Trim Bank 1 and Short Term Fuel Trim Bank 2. Numbers that far negative mean that the computer is metering fuel back out of the mixture due to a rich reading. You may have oxygen sensor issues or other fuel system issues, but that wouldn't be the cause of a P0128.

You are looking for the Engine Coolant Temperature (ECT) sensor reading. It may be in Celsius or may be in Fahrenheit, depending on how the OBD reader is configured. You're looking for the ECT sensor reading and the Intake Air Temperature (IAT) sensor reading. See if you can find those after the engine has been running for a while.
 

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More often than not we see vehicles with sticky thermostats that cause the problem. Temp sensors have tripped it but very rare.
 

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I just fixed this problem on my 03 by replacing the thermostat. When I took it out the rubber diaphram that is inside the thermostat was shredded. I put a new one in and the code hasn't been back.
 

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I cleaned off the sensor (there seemed to be some black stuff around it) and hit it with some compressed air and the light went away.
 
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