Mid 2010 Model A1278 / 2.4 or 2.66 GHz Core 2 Duo processor

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Liquid damaged MacBook running really slow. TN1D SMC IO Failed

I left my Macbook in my backpack and I guess my water bottle somehow opened and managed to get my Macbook wet. At first I wasn't getting any signs of life so I performed these steps on it to try to revive it:

1. Dropped the logic board into an ultrasonic cleaner to clean off corrosion. Afterwards, I submerged the motherboard into 99% isopropyl alcohol to displace the water and left it to dry overnight

*At this point, my Macbook is able to turn on but I notice that the fan kicks in at full speed and it's unbearably slow

2. I ran ASD on it and was able to get an "SMC IO Fail" error underneath TN1D. I did a bit of research and found out that TN1D represents the MCP 0 Die Temp.

It sounds to me like it's a faulty sensor. However, I don't know where this is on the motherboard. I have the schematics and boardview for it but it doesn't mention anything about MCP 0 Die.

3. I measured the resistors around the sensors and they all measured as they're supposed to. I checked the voltage rails too and they are measuring correctly as well.

4. I reflowed the SMC chip with an hot air gun but still the same result.

I'm am now stuck. Could someone please point me in the right direction?


I looked at the schematic again and found MCP T-Diode Thermal Sensor. I ended up taking off this chip and putting it back on and it then it passed the ASD test! However after a few minutes, I ran the test again and it failed.

I ended up ordering a new MCP Thermal Sensor chip for the board. I'll replace it once I get it. Hopefully this works.


Replacing the SMC Thermal Diode did not seem to work. It still gives me the same error which is the TN1D error. Does anyone have any suggestions?

Answer this question I have this problem too

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Might seem silly but have you reset the smc

also it could be the smc that needs replacing as this is a common fault with water damage


Can you tell me where I can find the SMC? I searched for it but cannot find it anywhere. I'd like to order it and try replacing it.


Look for it on Ebay or China's ali, using your board number, MacBook Pro A model number, and year. As all those will help you determine that you are getting the correct part. You should get it on a board to make sure it is Apple original and programmed to match your board. Even better, try to get it reballed. Reballing it is a pain unless you have the stencil.

I can't confirm that the SMC is faulty as I don't know the subject enough to diagnose it without having the board on my bench, but at least look up the SMC in the schematics and check that all in and out lines are measuring correctly for voltages and resistivity of the resistors, and no shorts to ground.


Most board re-workers pull SMC off of donor boards, not all work sometimes we have to do this a few times these chips are programmed, they need to be re-balled either with spheres or paste using stencils.


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1 Answer

The MCP Thermal Sensor/Diode is inside the MCP chip itself. MCP_THMDIODE_P and MCP_THMDIODE_N are the two data lines that connect U5535 to the MCP. The chip that connects the thermal diode to the SMC: connects to a thermal diode inside the MCP (called MCP Die), and also houses a separate thermal sensor called MCP Proximity.

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