MacBook Pro M1 2020 - 820-2020-A - 20V in one port and 5v in the other

[TimScrawn]

Got a bit of a strange one here. Issue is that the mac powers on and charges just fine in one of the ports. When you plug the cable into the other, it will sit at 5v but still draw 2.3 amps, just like the 20v port.

Board is just like brand new, no liquid damage or anything. Has been swapped into a new housing previously though by another shop. Was given to the customer and they brought it back to them saying it wasn't charging correctly.

Checked board measurements. I have also tried the charger flipped both ways for the CCX pins, but still makes no difference.

Diode Readings:
USBC0_CC1 - 0.590
USBC0_CC2 - 0.590
USBC1_CC1 - 0.591
USBC1_CC2 - 0.591

I have also checked the ESD diodes and they are look jsut fine with correct readings? I'm now a little stuck... Could this be a tbt rom issue? Or a PD issue?

Thanks

[TimScrawn]

Hi Mon,

I have just replaced the PD controller and the USB C port is now working! So it seemed to be PD controller related... Maybe a communication issue with the PD controller? Didn't look bad underneath? Maybe could have reused the same chip...

Al good now though. Thanks for you help though. Really appreciated!

[mon2]

CCx lines look ok to me.

Could the contacts of the non-working side have debris / cat urine on them? Clean them up good with IPA (alcohol) & Q-tips.

[TimScrawn]

Hey bud,

Thank you for responding so quickly to this. Yeah, I have tried cleaning out the FPC connector. This is the 13 inch m1 so only one set of usb c ports on one side. FPC connector very clean. I have check continuity from CCX pins to the test pads as well and it all seems good. A very weird one really...

[mon2]

Is the current draw an immediate 2.3A on the bad port or climbs up to this value? If immediate, you have a shorted cap or similar on this port. I would check each of the LDO rails on the non-working port. Ideally compare the rails against the working port. In the end, the PD controller is a stand alone microcontroller (Cortex Mx series) with firmware to select the 20v.

If available to you, use a PD analyzer tool to snoop on the traffic. At least see if the non-working tool is able to extract the PD contract list from the mated power adapter. I think the Qianli iBridge A3 tool can do this. You should be able to get this from Mobile Sentrix (UK) - we purchased a few of these to quickly diagnose incoming macbooks in our shop.

[TimScrawn]

Hi there,

Thanks again for responding. So the current draw on the bad port will climb slowly, as if it is working. So it will start at like 5v0.3 and then go to like 0.7, then 1.3, then 2.3 and then it will just drop to 0amp draw and sit like that. The other port works just fine. The mac also works just fine and when logged in, when using the bad port it displays as a charging symbol, but will specific that the battery is not charging correctly. Tried another usb c port as well in case, but still no difference... New charger etc...

I have just ordered one of those tools ,thanks for the recommendation.

Will check the LDO's in a little bit and report back. Thanks for the help so far!

[mon2]

It almost hints that the root cause is the PD controller itself. Will be interesting to see any traffic over the CCx pin using one port vs. the other. By design, each PD controller requests the full database of pd contracts from the power adapter. Known to be working for the one port but may not be the case for the non-working port.

Check the YT videos / media on the Qianli tool. It is versatile and should assist in the debugging.

[TimScrawn]

Thanks for the help again! Yeah, I started to think this could just be a problematic PD controller or possible TBT ROM. Would it be possible for it to be caused by a TBT ROM? Or is that unlikely? I think I might end up just replacing the PD controller and see if that changes anything. Unfortunately, I need to get this job finished even if its not a fix. So won't be able to hold off until tool arrives. I will report back if this changes anything. I have seen similar things where people have not been able to enter DFU mode on an m1 mbp but the pd controller itself works just fine in terms of charging. Replacing the PD controller fixed the DFU issue... So maybe its one of those weird cases where the mac still works, despite there being an issue with the PD controller...

[TimScrawn]

Hi Mon,

I have just replaced the PD controller and the USB C port is now working! So it seemed to be PD controller related... Maybe a communication issue with the PD controller? Didn't look bad underneath? Maybe could have reused the same chip...

Al good now though. Thanks for you help though. Really appreciated!

[mon2]

Very good. From where did you source the replacement pd controller? Donor board? Same location or AliExpress? Good to hear a success story and the details of the repair.

[TimScrawn]

I sourced from a donor board. It was a PD controller I had laying around with other chips I had previously pulled, so unable to verify if it was from the same model or position. New type of fault for me. Never seen something like this before to be honest. Seen similar cases where the mac won't enter DFU because of a bad PD but it will charge etc... But not something like this...