Mac sensors reference designators

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SMC sensor codes (reported in ASD) can be quite cryptic and there is no way to immediately know which component it refers to on the logic board. Some schematics have the sensor code next to the component, some don't. Some schematics tell the description for a group of sensor, some give a hint on the placement, but sometimes it is wrong.

Remember that when you have an issue on an SMBUS, you will have multiple sensors showing an error, all related to the same sensor hub on that specific SMBUS, but it may be caused by something else (eg. ALS or Touchpad).

Warning: this is a work in progress. The information here has not been exhaustively verified! This is mostly guess work from the information in the schematics, the boardviews, the ASD sensor lists and reports of correlation between sensors found on the web.

Warning 2: when using a monitoring software such as HWMonitor, the sensor descriptions may be wrong. It may even hide some sensors and show missing ones.

List of abbreviations used in sensor descriptions

  • TBT = Thunderbolt
  • T29 = Thunderbolt controller
  • MLB = Main Logic Board
  • BOT = Bottom
  • TBD = To Be Determined (ie. no information in this schematics revision)
  • BMON = Battery Monitoring
  • AMON = AC Adapter Monitoring

MacBook Air

MacBook Air 11" 2013 820-3435

Matching between reference designators and sensor description is different from the MacBook Air 13" 2013 820-3437.

MacBookAir6,1 in SMC Sensor Codes.

Schematics contains gives wrong hints about sensors.

Temperature sensors
SMC Sensor Code Description Reference designator Bus
TS2P Memory Proximity Q5810 SMC S0 "1" SMBus
THSP T29 Proximity Q5820 SMC "3" SMBus S0
Ta0P Inlet Q5830 SMC S0 "1" SMBus
TW0P Wireless Proximity Q5840 SMC "3" SMBus S0
TM0P Camera Proximity Q5850 SMC "3" SMBus S0
TCHP Charger Proximity Q5860 SMC S0 "1" SMBus
TC0P CPU Proximity U5800 SMC S0 "1" SMBus
Tm0P Logic Board Top Side U5810 SMC "3" SMBus S0
Ts0P Trackpad J4800 SMC "3" SMBus S0
TB0T Battery J6950 SMC "5" SMBus G3H
TB1T BMU 1 J6950 SMC "5" SMBus G3H
TB2T BMU 2 J6950 SMC "5" SMBus G3H
Th1H Fin Stack J9500 SMC "2" SMBus S3
TCXC CPU Core PECI U0500 PECI
TPCD Platform Controller Hub U0500 PECI

MacBook Air 13" 2013 820-3437

MacBookAir6,2 in SMC Sensor Codes.

Schematics contains gives wrong hints about sensors.

Temperature sensors
SMC Sensor Code Description Reference designator Bus
TS2P Camera Proximity Q5810 SMC S0 "1" SMBus
THSP T29 Proximity Q5820 SMC "3" SMBus S0
Ta0P Inlet Q5830 SMC S0 "1" SMBus
TW0P Wireless Proximity Q5840 SMC "3" SMBus S0
TM0P Memory Proximity Q5850 SMC "3" SMBus S0
TCHP Charger Proximity Q5860 SMC S0 "1" SMBus
TC0P CPU Proximity U5800 SMC S0 "1" SMBus
Tm0P Logic Board Top Side U5810 SMC "3" SMBus S0
Ts0P Trackpad J4800 SMC "3" SMBus S0
TB0T Battery J6950 SMC "5" SMBus G3H
TB1T BMU 1 J6950 SMC "5" SMBus G3H
TB2T BMU 2 J6950 SMC "5" SMBus G3H
Th1H Fin Stack J9500 SMC "2" SMBus S3
TCXC CPU Core PECI U0500 PECI
TPCD Platform Controller Hub U0500 PECI

MacBook Air 13" 2015 820-00165

MacBookAir7,2 in SMC Sensor Codes.

Warning: HWMonitor may show a non-existent "Meomory Proximity" and hide "Thunderbolt Proximity"

Schematics contains gives wrong hints about sensors.

Temperature sensors
SMC Sensor Code Description Reference designator Bus
TS2P S2 Camera Proximity Q5810 SMC S0 "1" SMBus
THSP T29 Proximity Q5820 SMC "3" SMBus S0
Ta0P Air Flow Q5830 SMC S0 "1" SMBus
TW0P Wireless Proximity Q5840 SMC "3" SMBus S0
TM0P Memory Proximity Q5850 SMC "3" SMBus S0
TCHP Charger Proximity Q5860 SMC S0 "1" SMBus
TC0P CPU Proximity U5800 SMC S0 "1" SMBus
Tm0P Logic Board Top Side U5810 SMC "3" SMBus S0
Ts0P Trackpad J4800 SMC "3" SMBus S0
TB0T Battery J6950 SMC "5" SMBus G3H
TB1T Battery Sensor 1 J6950 SMC "5" SMBus G3H
TB2T Battery Sensor 2 J6950 SMC "5" SMBus G3H
Th1H Fin Stack J9500 SMC "2" SMBus S3
TC1C CPU Core 1 U0500 PECI
TC2C CPU Core 2 U0500 PECI
TCGC Intel GPU U0500 PECI
TCSA CPU System Agent Core U0500 PECI
TPCD Platform Controller Hub U0500 PECI

Repair section

In most cases failed sensors is rather a communication line problem. Since it is shared between multiple sensors, it might cause lots of different issues. For example, failed ALS sensor on the display side might cause malfunctions of amost all thermal sensors on board, simply because it is pulling shared SMC SMBus line to ground.

820-3437-B multiple sensor issues

The problem:-

70% CPU usage when idle, machine slow and you may need to hold the power button to get the system to boot, however, sometimes the system still fails to power.

ASD faulting sensors (IC0R, ID0R, IM3C, ISDC, PB1R, PC0R, PDTR, PPBR, PSDC, VC1C, VCS0, VP0R). Device takes 0.06MAh.

Issues found/fixed:-

PBUS_S0_VSENSE missing - Q5500 Pin 3 via severely corroded. Ran jumper to R5503 Pin 1 to restore, issues persist.

C5021 turned into 1Ω. Capacitor replaced, issues resolved, and ASD passed diagnostics.

Addition:-

I had an issue with C5021 again (21st September 2021) and this time the machine would not power on and PM_SLP_S4_L was missing. A quick check of C5020, C5021 and C5125 showed they were shorted to ground through C5021. Replacing C5021 (1uf X5R 0201) fixed the issue and the machine boots again. If there is a short in this area, it can cause all sorts of issues.