Apple MD094LL/A Manuale Utente

iMac (27-inch, Mid 2010) — General Troubleshooting 

2010-09-09

The following diagnostics are required for this product:
•  Apple Service Diagnostic (ASD), version 3S140
•  For iMac (27-inch, Mid 2010): Apple Hardware Test (AHT), version 3A202
•  Bluetooth Service Diagnostic (BSD) 1.1

Run latest available service utilities to determine if any thermal sensors or blowers are malfunctioning. When a 
test reports an error, reseat appropriate connections and check that all air flows are free from obstruction.  If issue 
persists, replace the corresponding part (sensor, blower, logic board, video card, or power supply). See chart below 
for correlation between affected sensor, sensor location, and additional checks to perform. 

Note: AHT can be run by pressing the D key on startup (if hard drive was not reformatted, or if adequate system 
specific restore DVD is inserted). If a sensor error is detected, AHT will report an error code containing the affected 
sensor name (ex: “4SNS/1/40000000 TC0H” error code reports to sensor TC0H). 

TA0P

Excessive incoming Ambient air 
temperature, or Ambient temp 
sensor damaged/disconnected 
from logic board. 

Verify that incoming/outgoing air vents 
are free from obstruction , that sensor 
cable is securely connected to the top 
edge of the logic board and attached to 
the left speaker housing. Replace sensor 
cable if damaged.

All fans ramp at full 
speed if sensor is 
disconnected.

T00p

Excessive Optical Drive area 
temperature, or ODD temp 
sensor damaged/ disconnected 
from logic board.

Verify sensor cable is securely connected 
to the logic board and the sensor 
is properly attached to the ODD 
mechanism. Replace sensor cable if 
damaged.

The ODD fan will run 
at full speed if sensor is 
disconnected.

TH00

Excessive Hard Drive area 
temperature, or HDD temp 
sensor damaged/disconnected 
from logic board. Use the 
correct sensor cable, each drive 
vendor has a unique sensor 
cable model.

Verify sensor cable is securely connected 
to top left side of logic board and it’s 
connected to hard drive.  Check for 
damaged cable on logic board. 

The HD fan may run at 
full speed if the sensor 
is disconnected. 

Tm0p

Excessive logic board 
temperature (this sensor is part 
of logic board)

Test with known-good logic board

TL0p

Excessive LCD panel area 
temperature, or  LCD temp 
sensor damaged/disconnected 
from top of logic board

Verify that the LCD sensor cable is 
securely connected to the logic board 
and the sensor is attached to the LCD.  
Replace the sensor cable if damaged

The CPU fan will run at 
full speed if the sensor 
is disconnected.