MacBook Pro 16-inch M1 Pro: 140W adapter power connection issue

Welcome!

This seems a bit odd for a 16-inch (2021), M1 Pro:

• Battery health: Normal, 100% maximum capacity, 12 cycles

Is that the original battery? If so, those stats look very suspect for a Mac model that was discontinued nearly four years ago. Has the battery been replaced? If an old battery or a non-Apple replacement, that could be a factor but doesn't explain why the same battery is happy with a lower-power charger.

From your thorough report, it sounds like it is something within that charger. My M4 Pro 14" has the 96W version and has worked without issue for over 18 months. The only other test option I can think of is to replace the removable AC wall socket adapter with Apple's 6-foot Power Adapter Extension cable. I've accumulated four of these treasures, and at US$ 19, they are too useful not to have with your kit.

Power Adapter Extension Cable (AC Connector 2)

You'll need the "2" version"for the 140W adapter. They are great for travel where you never know how far an outlet may be from where you would like to use your Mac.

Did replacing the 140W adapter, changing the MagSafe cable, or updating macOS resolve the issue for anyone?

I don't see every post here but I see a lot of them. I do not recall a similar issue reported here.

Keep us posted, please!

Cheers!

Allan

kutz777 wrote:

MacBook Pro 16" M1 Pro (2021): repeated power connection events during sleep at 100% battery — Apple 140W adapter or firmware issue?

Hi everyone,

I'm trying to determine whether I'm dealing with a faulty Apple 140W power adapter, a macOS/firmware issue, or a hardware problem inside my MacBook.

I haven't been able to test another known-good high-wattage adapter yet.

Any experiences or suggestions would be appreciated. I'm particularly interested in whether others have observed the same behavior after recent software or firmware updates.

Did you just buy this Mac??? or it is an old issue...

Is this a replaced battery or OEM? Cycle count of 12 does not sound right as mentioned by Allan Jones.

Anywhere in there do you say what exact macOS you are running?

verify your software is up to date—The current stable release includes bug fixes.

Current Tahoe 26.7.2

Current Golden Gate 27.2 (edit: I see it now "macOS 27.2)

A SafeBoot https://support.apple.com/en-us/HT201262 will sort many anomalies

certain system caches get cleared and rebuilt—Reboot as normal and test. If this did not sort your issue I would get my hand on another magsafe and compare your results.

Try the user Diagnostic while you are plugged into your power source/troubled MagSafe...

may kick out an error code.

Use Apple Diagnostics to test your Mac for hardware issues

https://support.apple.com/en-us/HT202731

Best Buy has a generous return policy...

In or out of warranty you can get a free over the counter 'Apple Service Diagnostics' test /assessment

Make an appointment for a "hardware issue"

https://www.apple.com/retail/geniusbar/

Outside the USA

https://support.apple.com/en-us/HT201232

kutz777 wrote:

Thank you everyone for your replies.

Just to clarify a few points:

I purchased this MacBook Pro brand new in March 2026, although it is a 2021 model. As far as I know, the battery is original. I use the MacBook mainly connected to external power, which may help explain the low cycle count.

I have already tested Safe Mode, and the MagSafe issue still occurs there. Apple Diagnostics reported no errors.

I also tried replacing the removable AC wall plug on the 140W adapter, but that did not help.

The most interesting finding is that the repeated power-related events occur with my 140W adapter through both MagSafe and USB-C, while they were absent during comparable tests with 20W adapters.

I agree that testing another known-good Apple 140W adapter would be the most useful next step. Unfortunately, I don't have access to one yet.

I have also ordered an original Apple 35W adapter for an additional comparison.

Thanks again for your suggestions. I'll update the thread when I have more results.

You are still under the 1-yr warranty if purchased new. Why hesitate to get it resolved...Take it in let Apple tell you what is the issue.

The MagSafe charger is covered under the hardware warranty as well as the battery.

If the battery has sat unused for 5 yrs (2021) it could be the issue.

Not sure where you would even buy a "new" 2021 M1 (?) unless old inventory stuck on some shelf somewhere.

ref: https://checkcoverage.apple.com

Hi,

You should take your MacBook Pro to your local retail AppleStore, Genius Bar or Apple Authorized Service Provider to check your MacBook Pro as well as AC Adapter there.