CPU throttling sensor error code: 4SNS/1/C0000008: Th1H- -124
I found my Macbook (MacBook Air 13" Mid 2012 A1466 EMC 2559) was running very slow (slow boot, login, mouse lag etc.) and its fan was running fast. It was like this even when it was cold, no programs were running, and when on the login screen.
I looked in the activity manager and found that kernal_ task was at high CPU usage (>300%). I looked this up using Google and found that this is how Mac CPU throttling is done.
I have also noticed that if I wake the Macbook up from sleep, it will run fast for about the first 20 s then go back to being slow and the fan will speed up.
I ran the Apple Hardware Test (version 3A239) and found the error code 4SNS/1/C0000008: Th1H- -124 which I have looked up and found that it is a heat pipe (heat sink) temperature sensor error.
I then installed Mac Fan Control fan app to see what the temperature sensors are reading. I found that the temperature readings looked fine:
SENSOR VALUE (°C)
Battery Max: 26.2
Battery Sensor 1: 30.1
Battery Sensor 2: 30.6
CPU Core 1: 36.4
CPU Core 2: 35.0
CPU Core 3: 38.0
CPU Diode: 33.1
CPU PECI: 36.4
CPU Proximity: 28.1
GPU PECI: 37.0
Memory Proximity: 28.8
Palm Reset: 21.1
Platform Controller Hub Die: 44.0
APPLE SSD TS128E: 28.0
I have reset the PRAM and the SMC but this did not change the throttling and fan speed, and I still get the 4SNS/1/C0000008: Th1H- -124 error code.
I opened the Macbook up to see if anything near the heatpipe looked bad but I could not find anything. I removed the heatsink from the CPU to check the thermal paste and found that it was a bit dry so I replaced it.
I reset the PRAM and SMC again and reran the hardware test but this did not change anything either.
I think it is strange that I am getting normal temperature measurements using Mac Fan Control app but still getting the error code. Is this sensor’s value not displayed here?
I want to find the heat pipe temperature sensor and maybe try to reflow it but I don’t know where it is.
Does anyone know where this heat pipe temperature sensor is located?
Any other ideas on how to fix this issue would be greatly appreciated.
Thanks for your reply Reece.
I have had another look in the Macbook:
I found a bit of corrosion on one of the resistors underneath the main PCB:
Does it look like this corrosion might be in a location that would cause this sensor error?
Yes! the corrosion is on on of the sensor lines! That's likely the cause of your thermal sensor error. You may need to also replace the resistor.