DFU Mode Restore (Macs)
All MacBooks starting with T2 support this feature.
- 2018+ A1989/A2159 13" MacBook Pro
- 2018+ A1990 15" MacBook Pro
- 2019 A2141 16" MacBook Pro
- 2018+ A1932 13" MacBook Air
- 2018+ A1993 Mac mini
- 2017 A1862 iMac Pro
- 2019 A1991 Mac Pro
- 2020 A2338 13" M1 MacBook Pro
- 2020 A2337 13" M1 MacBook Air
- 2020 A2348 M1 Mac mini
- 2021 A2442 14" M1 Pro / M1 Max MacBook Pro
- 2021 A2485 16" M1 Pro / M1 Max MacBook Pro
- 2022 A2681 13" M2 MacBook Air
- 2022 A2338 13" M2 MacBook Pro
- 2023 A2779 14" M2 Pro / M2 Max MacBook Pro
- 2023 A2780 16" M2 Pro / M2 Max MacBook Pro
Scenarios for restore:
DFU mode is needed to restore the T2 firmware when:
- Failed macOS upgrade/reinstall/Security Update
- Failed Combo or Delta update
- Unable to boot into the current OS Internet Recovery using command + option + R
- Unable to successfully create computer account and log in after erasing and reinstalling (M1 computers specifically)
- Looping apple logo with no loading bar after waterdamage on power button (820-00850 confirmed case)
- CPU / PCH replacement: since ME+EFI image is located on BridgeOS partition, to do classical "clean ME" procedure after PCH swap, you need to do full DFU restore. Whis will put uninitialized ME image to BridgeOS partition. Revive is enough to perform CleanME, so if you swapped CPU for data recovery, you can first backup with Target Disk mode, then try revive and full boot.
- waterdamage on TouchID / Power button connector. One of weirdly common reasons for currupt BridgeOS firmware is corroded TouchID connector. It is hard to tell why, but many devices stuck in G3H/T2 state are being repaired after revive.
Other reasons to restore:
Essentially anytime you see something that communicates with T2 not function, a DFU restore may resolve. However, rule out other possibilities first!
A few examples:
- Battery communication lines being pulled down - but not short causing battery not being recognized and not charging. T2 handles SMC communications now.
- Raise/Wake not working properly. I've had two scenarios:
- 1: LID_OPEN_LEFT, LID_OPEN_RIGHT, and IPD_LID_OPEN would all function properly when triggered, however the unit would not sleep when lid closed. DFU restore fixed
- 2: (820-01958) SMC_LID_RIGHT was low - 1v1 instead of the 1v8 it should be. Causing the unit not to fully wake when raising the lid (did respond when lid was closed) The camera also did not work, which lead me to U4850. I replaced U4580, which fixed the camera, however the SMC_LID_RIGHT line was brought even lower to .110v I isolated the issue to T2. I attempted a restore, this did not work. I tied IPD_LID_OPEN to SMC_LID_RIGHT to put a bandaid on the situation. Obviously this way the unit won't functional properly.
The moral of the story here, is before you attempt a DFU restore, for something that could be T2, attempt to rule out everything else before the restore, as you could brick the unit, and be in a worse condition.
Beware of the risk!
Rule out parts or any other board issue that is possible before DFU restoring the unit. There are many things that can cause a DFU restore to fail. The problem is, if you fail a DFU restore, you may end up in a different error state than your original issue. For example:
If you have a board that comes in, with no power. You plug it into another unit, to check if its in DFU mode. It's not. Let's say PP3v3_G3H is shorted. Let's call this Failure State A.
Now you're in Failure State A, and you decided to force the unit into DFU, and attempt a restore. At this point, it would fail, and you would be stuck in recovery, let's call this Failure State B. Now you're at Failure State B, it makes it 10x harder to diagnose Failure State A, simply because you can't follow the power structure anymore. At this point, if you find you're short on PP3v3_G3H and remove it, you would have to restore again and PRAY that it works. It does not always. There have been many cases, where the unit came in with liquid damage, clearly a Failure State A type of situation, but the client attempted to restore before sending it, making it into a Failure State B. It seems half the time, after I fix Failure A, that I am able to get out of Failure B after restore. The half that is unsuccessful, is, I'm sure because of a damaged trace or something like that - however, with it being in recovery, or Failure State B, it's much harder to diagnose.
DO NOT DFU IF TARGET MAC IS ON BETA SOFTWARE. THIS WILL BRICK THE MAC AND YOU WILL HAVE TO DO THE WALK OF SHAME TO AN APPLE STORE.
Most boards require touchpad, some boards require Touchpad + Touchbar for full restore. Check trackpad on vaterdamaged devices before doing DFU Restore.
You will need:
- a host Mac which has minimum OS of 10.13.5, Apple Configurator 2.6 or newer installed (from App Store), and an internet connection.
- USB-C cable which supports data, USB A to C cable, or Thunderbolt 3 cable.
- Target Mac (one that is being put in DFU) is connected to power. Do not use the left port closest to track pad for power - you will need this for data.
- Target Mac has charged and functional battery. After initial Phase of iBoot restoer (SoCrom) there will be issued a reset signal which cuts external power supply. If PPBUS voltage sinks below threshold, T2 will lose its power and reset into recovery mode. This usually seen as a "usb connection" error roughly after approx 30-40 sec. If something like that happens with your mac, monitor PPBUS / T2 SLP Voltages to confirm.
Make sure Host Mac is powered up, iTunes is not open if applicable (fully quit) and open Apple Configurator 2.
For Intel MacBook Pro and MacBook Air - Make sure Mac is shut down (hold power button for 5 seconds). Plug in data cable to Host Mac (any port) then into the left port closest to track pad in the Target Mac. Hold right shift + left option + left control + power keys simultaneously for about 3 seconds (according to Apple, other sources say 4-8 seconds). NOTE: We found that if you press the power button for 1 one thousand and then simultaneously hold the right shift + left option + left control, you should be successful each time. We also found that we were able to get in DFU mode around 4 to 6 (one one thousand, etc.) seconds. The Target Mac will remain as a black screen but you should see the DFU box pop up in Apple Configurator window on the Host Mac:
- ALTERNATIVELY if you only have a bare board, a bad keyboard, etc. you can force DFU mode by pulling SMC_FORCE_DFU up to 1.8V using the PP1V8_SLP_S2R line. Many boards have "debug buttons" to achieve this - for example RE032 on 820-00850. You can search through the schematic for SOC_FORCE_DFU and follow it to the debug page. Be sure to use the correct port or your host system running Apple Configurator 2 will pop a "Cannot Use Thunderbolt Accessory" message, indicating that it's either NOT in DFU mode or not connected to the correct port. Also, the system may fail to revive/restore properly if the connection is persistent - thus the use of a momentary-closed button in the schematic. You can just use a large piece of jumper wire, and once the target system is connected to the host system and appearing in AC2, you can just cut the jumper wire freely. (It's a bit of a juggling act, but you could also just use tweezers to make the connection temporarily... but I've found the jumper wire method to be 100% reliable and super easy.)
For M1 MacBook Pro and MacBook Air - Make sure Mac is shut down (hold power button for 5 seconds). Plug in data cable to Host Mac (any port) then into the left-side port closest to the screen in the Target Mac. Press the power button for about half a second, then also press and hold Left Control + Left Option + Right Shift for 10 seconds, then release all keys except power and hold power until the Target Mac shows up in Apple Configurator on the Host Mac.
For Intel Mac mini and iMac Pro - Disconnect power cord from Target Mac. Plug in data cable on Target Mac to port closest to the HDMI port. Hold down power button and plug the power cord back in. Continue holding power button for about 3 seconds. The Target Mac will remain as a black screen but you should see the DFU logo in Apple Configurator window.
My experience with A2179 Macbook Air / 820-01958. I had to force this machine into DFU by connecting SOC_FORCE_DFU (pin 1 R8010) line to PP1V8_SLPS2R (pin 1 C7840) I then connected this target Mac to the host Mac that has AC2 installed and opened. If I connect that cable to the rear left hand port closest to the screen, it does not show up as in being in DFU. However if I connect it to the front port closest to the trackpad (as what we do in Macbook Pros) it shows up in AC2 as being in DFU mode. Obviously then I disconnect the wire from PP1V8_SLPS2R to SOC_FORCE_DFU. I just wanted to share my experience with others as it conflicts with what is stated above.Nice if others can verify.
For M1 Mac mini - Disconnect Target Mac from power for at least 10 seconds. Plug in data cable on Target Mac to port closest to ethernet and into any port on Host Mac, then press and hold power while reconnecting power, then release power. The status indicator color should be amber.
For 2019 Mac Pro - Disconnect power cord from Target Mac. Plug in data cable on Target Mac to USB-C port farthest from the power button. While holding the power button, connect the power cord and continue to hold the power button for about 3 seconds.
NO DFU Mode Troubleshooting
- measure DFU_STATUS voltage. 1.8v indicates T2 is in DFU mode. In some cases pin might be shorted in T2 and needs external Pullup so CD3215/17 would be switched into DFU.
- If DFU Status is high but device is not visible with known good cable - inspect TBT ROM and CD3215/17. To properly allow DFU Connection CD321* should be initialized and TBT rom should be loaded. If you suspect TBT controller, remove SPI straps betweeт TBT SPI ROM and TBT Controller.
- if DFU_status is low, inspect if T2 is fully powered and receivesd signal. The easiest way to get DFU is described below.
100% direct DFU mode using jumper
- locate FORCE_DFU jumper. on some Macbook Air boards there is just a testpoint which needs a wire to connect it with 1.8V. This signal needs to be pulled up to 1.8v to activate FORCE_DFU
- power-reset the device (unplug the battery, plug it back).
- Pull FORCE_DFU to 1.8v line
- connect DFU cable to the device. It will both activate and autostart the macbook which will act as a proper "power button" trigger, switching the device straight into DFU.
This results DFU mode in 10/10 cases unless there is something wrong with T2/Jumper/CD321*/Cable
Complete the restore through Apple Configurator. When done, verify that the process completed.
Few things from experience (inwerp):
Case: Macbook Pro 2018 15', 5V shortly 0.3A, than 0.04A-0.08 floating, all G3HOT present. Died with no particular reason, stopped charging and simply did not start up after next reboot.
- Did not work with USBA-USBC adapter (claimed to work by Apple Article), used thunderbolt cable.
- Apple Configurator shows DFU logo without key combination, but flashing in this mode will end up with a undefined error.
- Key combination works like 50/50, no particular pattern, best looks like DFU LOGO - SMC RESET Combo 4 Sec till DFU Logo disappears, shows again, now flashing works.
may end up with the connection timeout, target device will start to boot, then shutdown at some point.
Macbook Pro 13 2019 820-00850
After minor liquid spill on power button / cd3215 chip. After cd3215 repair device freezes on apple logo without progress bar, does not boot into internet recovery. For some reason DFU Restore fixed the device, probably waterdamage on power button connector might somehow damage BridgeOS?
Few things from experience (Liminalsunset):
DFU Restore on T2 Mac: MacBook Pro 16" 2019
It's possible to restore the T2 firmware on this machine using a MacBook Air, Mid-2013 13" laptop. It appears that a USB-C mac is not required to initiate the process.
Both systems were running Catalina 10.15.7. This does erase the SSD. I used Internet Recovery to restore a backup and it worked fine after. Activation Lock and FileVault were enabled prior to procedure and do not appear to affect it. Works with Target MacBook Pro powered off of battery.
To enter DFU mode I used:
1) Turn off MBP and plug in USB A to USB C cable (third party) from MacBook Air into MacBook Pro, port closest to you facing computer on the left side
2) Locate left Control and Option keys on MacBook Pro, as well as right Shift key.
3) Press Power button for 1 second, then hold keys above down with power button for 8 (real) seconds. MBP will flash Apple logo, then it will disappear
4) DFU device should show up in Apple Configurator 2. Rest of process is uneventful and works normally. Once restore is complete MBP may need manually powered off and on to start into Internet Recovery
Few things from experience: (Dusten Mahathy)
Unit not booting without battery present. This board will boot on a 96watt adapter normally. I have seen 3 cases where the board doesn't boot on the adapter alone, and wouldn't charge a stone dead battery normally.
Without battery connected: 20v with a jump to 300-500mA then back to 70mA and kind of sit there.
With battery connected: It would very slowly raise to charging amperage. (It would take 2 to 3 minutes for it to reach 4 and a half amps, vs the normal 30 seconds to a minute)
After diagnosing the charging circuit, and seemingly everything on the board is physically okay, I decided to DFU restore the unit, thinking something with the SMC, that T2 is now handling.
This resolved the issue.
Prohibition Symbol: This seems to be caused by the board being disabled. Flashing the T2 ROM, and restoring via DFU resolved the issue.
Few things from experience: (Ed Hallman / crumblenaut)
Exact same deal as Dusten's Case 1 above - 820-01700 board, user reported crashing after liquid exposure and previous board-level work, eventually ending with the system not booting even WITH the battery present. With no battery we saw 20v with a jump to 300-500mA then back to ~70mA and kind of sit there, and with the battery connected we saw a slowly raising charge amperage.
DFU REVIVE would fail with the error code 6, despite (going off of the table below) the fact that all SSD rail resistances were good and voltages were present.
After confirming that the user had a backup (thank the dark lord), I performed a proper DFU RESTORE and that got it powering on and booting again. After first boot with Apple logo the system would power off. Second power took some time with fanspin and nothing on the screen, then fans stopped, then fans spun backup and screen initialized. Cmd+Opt+R got it reinstalling right away.
DFU error codes and troubleshooting
1 - The trackpad is not connected (For successful firmware, the MacBook needs a connected working trackpad).
6 - Probably could not write BridgeOS into service partition. Most likely SSD failure. There might be one hot NAND. Common symptom - T2 does not turn on S5 rails at all. If you have it in revive mode, try restore (All data will be lost!).
9 - This error can have many causes, so quickly finding the cause of its occurrence is quite difficult. Here are some of the causes of this error:
- BridgeOS partition not found (Use restore instead of revive, will format SSD), NANDs partition corrupted, NAND chips damaged or some similar.
- Malfunctions on the processor itself or power lines of the processor / RAM. Also if there is no processor on the motherboard.
- Flashing without a part of the cooling system (heat pipe) on macbooks with a large TDP.
- T2 / SEP ROM mismatch (Different T2 and SEP ROM should be restored, not revived) or SEP ROM was damaged and needs to be replaced.
10 - Bad cable / unstable connection.
21 - Resolved with SoC ROM replacement. On macbooks with an M1 processor, this error also means problems with NAND chips such as:
- Failure of one or two NANDs.
- Mismatch between the NAND model and the reference designation on the board (When replacing memory chips, you no longer need to write anything to them using the programmer, just follow the model/place on the board).
- Attempting to restore from recovery after replacing NANDs (After replacing NANDs, it is possible to restore only from DFU).
35 - probably bad trace on one NAND, sysconfig block cofiguration => NAND mismatch.
75 - T2 booted in recovery mode (Revive wont work).
3004 - Bad or no internet connection on the MacBook.
3501 - (0xDAD) - target Mac is not connected to power.
4005 - SSD not detected error.
4013 / 6 - errors indicate bad NAND Sysconfig or wrong position.
4014 - T2 RAM error.
- also have seen a bad battery give this error.
4045 / 4042 - Timeout error.
If you have Lock sign but no power after DFU revive, it is safe to say that both T2 and SSD work fine and problem is on Intel side. inspect S0 rails, no power might be caused by short on something like 5v rail or something what is used for communication pullups. It is always a good idea to check if after T2 boot device goes to S5 /S0 state.
From Experience: (Dusten Mahathy)
The unit came in with slight liquid damage on U7650, U6940, and Q7660. Shorted was PP5V_G3S. The shorted component was U8245. After replacing U8245, I found that PP5V_G3S was 10v, instead of the 5v that it was intended for. After only a few seconds of having the board on again after replacing U8245, to check measurements, it was shorted again. At this point, I replaced U7650, Q7660, and repaired several traces and capacitors, resistors. Once again, replacing U8245. This time when powering on the board PP5V_G3S, was at its normal voltage. However, the unit still would not boot. Hovering about 20v 100mA. So after further investigation, I found PPVCCIN_AUX_PCH was not being generated. This was due to PPVCCINAUX_VCC being shorted to ground. This failed component was U7400. Which was powered by PP5V_G3S. So, after replacing U7400, I was making progress. The unit would start the boot process, getting 1v8 on PPVCC_S0_CPU for a second, then 0v, but pulsing. So on/off/on/off scenario. I found the pulsing started all the way back at PP1v8_SLPS2R. I did find, however, that if I removed R7210, R7220, and R7230 the system would be stable again. These are the three resistors that powers PPVCC_S0_CPU. At this point, I am pretty certain that I have some sort of CPU failure. Wether it be the CPU itself or not, I am not sure. I felt that it was, as I have a suspicion the 10v going through the CPU MOSFETs probably killed the CPU. However, as a last desperation, and for research, I decided to attempt to DFU the machine. At his point, it failed, and I got error code 9. This was somewhat expected, as all the power rails are pulsing currently. So what I decided to do, was remove the three resistors mentioned early, to make the system stable again. At this point, the DFU restore went through successfully. This leads me to believe that CPU failure can cause error code 9
TO check if device is in DFU state, check voltage on SOC_DFU_STATUS. This goes directly to CD3217 on this port to switch it in DFU mode. If T2 is switched to DFU mode, proper level is 1.8V
DFU_STATUS high but no DFU visible in Apple Configurator might indicate problem with TBT ROM or CD3217
Comprehensive guide: https://mrmacintosh.com/how-to-restore-bridgeos-on-a-t2-mac-how-to-put-a-mac-into-dfu-mode/