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Repair information and guides for the minor refresh of the Late 2018 MacBook Air, with the same model number (A1932) and EMC number (3184). This model features a True Tone display and a slightly revised battery.

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Bad temp sensor causing extreme throttling

I have seen this on a few machines, but this is the specific model I can remember it being an issue. Typically the machine was in disuse for some time (6 months or more) and when turned back on again the battery indicated service was necessary and the machine is running obnoxiously slow, fans are ramped up to full. I actually work for an AASP (often to my chagrin), but having access to their diagnostic suite has its perks. It always tells me that the TB0T sensor is missing and pops up an SMC based failure (this doesn’t usually mean the SMC failed, just that it’s not communicating with something it’s supposed to be). I assume that throws the SMC into a tizzy and everything throttles down since the machine isn’t getting information from a temp sensor. But nothing is actually overheating, it’s just mad because this battery sensor isn’t talking to it.

Is there anyway around this aside from replacing the battery (which has always corrected the problem in my experience). Is there some way to tell the machine to just ignore this particular sensor? Or is this even advisable, if it can be done?

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TB0T - Battery - J6950 - SMC "5" SMBus G3H

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The SMBUS_3V3_BATT_SCL & SMBUS_3V3_BATT_SDA lines from the battery is the issue. Replacing the battery is the needed correction. Sorry I can’t see any way to over ride this.

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No need for apologies. Can't always be a software fix for a hardware problem. I was mostly just being nosey and despite being an AASP we are not just flush with known good parts, especially on newer models. So when I get these sort of issues and the machine is throttling so badly that just logging in takes 5 minutes I lose patience quickly. And since ruling out hardware is in the “luck of the drawer” (that we keep all the units that have been effectively abandonded in) it's not always easy to say definitively. Yep. Thats the problem. I am still learning how to make sense of schematics (that I can't really use to their full effect at work because the almighty Fruit God has deemed it so). But this makes total sense. Thanks for the help!


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Alisha C will be eternally grateful.
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