Dell U3419W connected via USB C keeps scanning for signal when MacBook is sleeping

Apparently Apple broke something after 10.14.3. We have been communicating with dell on a similar thread (https://www.dell.com/community/Monitors/U3818DW-USB-Type-C-power-delivery-problem/td-p/7452974/page/2) and their community manager posted that After 10.14.3 Apple broke compatibility with the controller that is used on the U3419W and U3818DW and that Dell cant do anything about it.

"With the release of Apple OS Mojave 10.14.3, Apple introduced a hardware incompatibility issue with our TPS6598E power delivery controller in the U3419W and U3818DW. When connected to the U3419W and U3818DW via the USB Type-C to C cable, if you update the Apple OS to Mojave 10.14.3 or later, you will see the following issues =

* Fully charged Apple MacBook constant "charm" sound due to waking and sleeping

* The monitor will display, "Scanning for Signal"

There will not be a monitor hardware power delivery controller upgrade to correct this hardware incompatibility issue created by Apple. You will need to back down the Apple OS to High Sierra 10.13.6 or earlier.

I received a Dell internal email which stated = There is not workaround to solve the incompatibility with the TPS6598E power delivery controller and the Apple OS 10.14.3. We do not see the issue on Apple OS 10.13.6 and Apple OS 10.12.6."

At the bottom of this U3419DW dell support thread , someone wrote that the U3818DW has a known USB-C PD defect that causes similar behavior when running the same firmware and may be the same issue:

The U3818DW running firmware M3B106 has a defect in the USB-C PD protocol that violates spec and causes similar sleep wake issues. This may be the same issue given M3B106 is the also the latest firmware for the U3419W and the symptoms are similar. See https://www.dell.com/community/Monitors/U3818DW-USB-Type-C-power-delivery-problem/td-p/7452974

If Dell is violating USB-C PD protocol this has nothing to do with Mac vs. PC and really a bug Dell needs to fix.

The linked thread has a USB-C PD dump that shows exactly what the U3818DW is doing wrong:

The Dell U3818DW trace shows how the monitor violates USB Type-C PD protocol and causes a infinite sleep/wake loop:

# Laptop waits ~1 minute, then sends a 3A max current request

0,v2.0,635,2:00.591.836,625.000 us,10 B,,2,Sink:DFP,[2]Request,62 14 2C B1 04 13 CB 3E 34 AF

# Monitor acks the request from laptop

0,,639,2:00.592.359,495.000 us,6 B,,2,Source:UFP,[2]GoodCRC,41 05 34 98 D1 D8

# Monitor Accepts laptop request

0,v2.0,642,2:00.593.160,491.000 us,6 B,,2,Source:UFP,[5]Accept,43 0B B1 D7 5F 0D

# Laptop acks accept from monitor

0,,645,2:00.593.693,496.000 us,6 B,,2,Sink:DFP,[5]GoodCRC,61 0A 07 A1 EA DD

# Monitor violates USB-C protocol by failing to send PS_RDY within 35ms, laptop times out after ~121.3ms and hard resets the link

0,,648,2:00.714.550,276.000 us,0 B,,2,,Hard Reset,

So I came here with the exact same problem. Brand new Dell U3419W out of the box and I'm connected to two machines:

• MacBook Pro > USB-C
• Mac Mini > Displayport

I also have USB-C charging set to "ON" when the display is off. But I don't think that setting makes a difference because that's just saying your computer will charge when the monitor is turned off—Has nothing to do with this issue.

Issue: While on my Mac Mini (Displayport input), I was getting USB-C "unplugged" / "plugged" notices from the Dell monitor, about every 30 secs to a minute. The MacBook Pro was triggering this. Checked the cable and everything seemed to be fine.

I've solved the issue by going to the MacBook Pro and turning off Energy Saver features for Power Adapter mode. It's up to you what settings you want for Battery too:

[ENABLE] Prevent computer from sleeping automatically when the display is off

I think this is the key setting. Sleeping any macOS machine is BAD if you want connectivity to certain devices to stay persistent.

[Disable] Put hard disks to sleep when possible

Turn this off. It's probably not relevant to this display issue, but this can also cause connectivity issues with devices that use your disk (e.g. If you're a video editor)

[Disable] Power Nap

This should always be off, regardless of this display issue. It's a terrible feature that causes a lot of problems with apps and device connectivity. I'd guess that this is what was causing the problem... Every time you got the spotty connection warning, I bet the computer was doing it's periodic checks for email or whatnot, turning itself on briefly, triggering the monitor. I would guess that this also affects the "Auto" input switching—If you have that turned on, Power Nap would be switching your inputs when you don't want it to.

Annoyances, but I think they're solvable :) Hope this helps!

I can tentatively confirm that @dvdswrd's solution works.

Disabling Power Nap seemed to decrease the frequency of the power connected sound, but it didn't entirely fix the issue.

Enabling "Prevent computer from sleeping automatically..." was the key, as he noted in his post. It's been about a week since I followed those instructions and I haven't heard my MacBook Pro make the power connected sound when it wasn't supposed to. I tested this with the Dell display turned off and with the Dell display turned on but asleep, and it seems to be fixed. 🙌🏻

did you try this solution form the Dell support conversations you linked?

<<I set the Monitor Sleep option in the display's OSD to "Never".>>

Any other displays I had with USB ports were searching for a signal, but not waking up the computer while still powering the device. I think the problem is that, when the monitor goes in sleep mode, the USB hub is powered down, so when it wake up to search for a signal, it power up, giving the mac the impression it was plugged into a power source, and wake it up.

I should have an option in the personalize menu with the latest firmware to let the USB power on while the screen is turned off, but I don't have it even if I have the latest version of the firmware...

The updated firmware for the Dell U3419W offers the option to keep the USB-C power on even when the monitor is powered off. the firmware update tool is dated August 19.

Update the firmware on the monitor (follow instructions)

Access the on screen menu, go to Personalize, USB-C Charging to enable

Try connecting the MacBook Pro power adapter to see if that will stop the display from attempting to charge and making that noise.

Dell is wrong to blame this on Apple. It may be true that things worked before 10.14.3, but Apple's USB-C PD behavior after 10.14.3 is still legal and Dell's USB-C PD behavior is clearly illegal. The fault lies on Dell's side.

The USB-C PD protocol traces in the U3818DW USB Type C power delivery problem thread clearly show that the Dell U3818DW monitor is violating USB-C PD spec and the Apple Macbook Pro's USB-C PD behavior is legal. Page 29 of the Dell UltraSharp U3818DW Monitor User’s Guide says "The USB Type-C power delivery compliant port (PD Version 2.0) delivers up to 100 W of power." so Dell either needs to fix this or stop advertising their monitor as USB-C PD compliant because it clearly isn't.

The same issue affects the Dell U3419DW, see the U3419W USB Type C power delivery problem thread. Page 32 of the Dell UltraSharp U3419W Monitor User's Guide says "The USB Type-C power delivery compliant port (PD Version 2.0) delivers up to 90 W of power."

I wonder if this something Apple could take up with the USB-IF compliance group?

For me it made the issue worst, so I deactivated the power option. At least, I can turn off the monitor so it stop waking up all the time. I will not use the monitor anymore as a USB hub and charger... Really bad, it will be my last Dell monitor.

When the display is powered on, but does not receive a signal, it is predictable behavior that it would scan for a signal. That message is coming from the microprocessor in the display, not from your Mac.

I do not understand how this is a defect, can you help me understand? what did you want the display to do?