Macbook Air M1 2020 A2337 - running on reserve battery (without battery)

[BMCappelletti]

Hi everyone.
Quick backgrounhd story: Macbook came to me stuck on 5V. According to repair.wiki I could have an issue on L7800. Indeed it was not passing signal through. And I did have an issue on PP5V_BSTLQ_VOUT_SPMU line. I found a cracked cap (C7800) and replaced both failing components.
Now it negotiates 20V and the computer starts, but I receive the message "you are now running on reserve battery power", as shown on the attached picture. It happens with or without a battery connected. So I am discarding a battery issue, for now (it may be bad, but I will only know for sure when this message stops appearing without a connected battery).
The battery icon has no power icon on it or anything else.
I cannot reinstall system, cause it prevents me from doing it with a low power battery.
I've searched for this error and all I could find were people with the legitimate message showing up, when indeed battery was low.
Any clue on where I should check for errors first:
Thanx.

[mon2]

What is the voltage to ground on:

CHGR_AUX_DET ; used to detect the power adapter

C5220 ; test each side

R5275 ; test each side

L5230

[BMCappelletti]

What is the voltage to ground on:

CHGR_AUX_DET ; used to detect the power adapter

C5220 ; test each side

R5275 ; test each side

L5230

C5220 20V each side

R5275 5V each side

L5230 fluctuating, from 4.x V to 11V

[mon2]

What is the voltage of CHGR_AUX_DET?

Remove all power. Disconnect the battery. Review the dual mosfets that surround L5230.

Measure the resistance for each mosfet:

source / drain
source / gate
gate / drain

Note again that there are 2 such mosfets inside each package. You may have to be creative to measure their tiny stub contacts. We use a single strand of wire from old IDE ribbon cables (PC days). Wrap this single delicate wire around a meter probe to make the wire tip a probe.

Testing if the mosfets are ok. Each should be hundreds of k ohms or higher else the dual mosfet may be defective.

[BMCappelletti]

What is the voltage of CHGR_AUX_DET?

Remove all power. Disconnect the battery. Review the dual mosfets that surround L5230.

Measure the resistance for each mosfet:

source / drain
source / gate
gate / drain

Note again that there are 2 such mosfets inside each package. You may have to be creative to measure their tiny stub contacts. We use a single strand of wire from old IDE ribbon cables (PC days). Wrap this single delicate wire around a meter probe to make the wire tip a probe.

Testing if the mosfets are ok. Each should be hundreds of k ohms or higher else the dual mosfet may be defective.

Used two needles, connected to alligator clips. Doesn't seem to have issues. I could not find shorts. Either OL or on the hundreds ohms.
For Q5240 pin 9 I used test point PPS5216. For Q5230 pin 10 I used test point PPS215.

For diagnosing this Macbook I used the penultimate case on this wiki: https://old.repair.wiki/w/A2337_2020_MacBook_Air
I had 0,03A and meter was cycling. And checking that information on the wiki I found the cracked cap and blown fuse. But I don't really get what is the PMIC they mention on it. Maybe there is a clue on it?

[mon2]

Post the measurements.

[BMCappelletti]

Post the measurements.

Guess it is all there.

Q5240
Pins 2 3 4
to pin 1 - open
to 8 - open
to 5 6 7 - 657 ohms
to 9 (PPS216) - 689 ohms

Pin 1
to 5 6 7 - 1030 ohms
to 8 - open
to 9 - 110 ohms, and going up

Pins 5 6 7
to 8 - open
to 9 - open

Pin 8 to 9 - open


Q5230
Pins 7 6 5
to pin 8 - 587 ohms
to pins 2 3 4 - open
to pin 1 - open
to pin 9 - open

Pin 8
to 2 3 4 - open
to 1 - open
to 9 - open
to 5 6 7 - 588 ohms

Pin 2 3 4
to 1 - open
to 9 - 686 ohms

[mon2]

The measurements are in ohms? Not k ohms? Confirm if the meter face shows 'k' ohms. If in ohms, these parts are defective. Suggest to flux (carefully) and remove them for another measurement check while the parts are removed from the board. Share the measurements again.

[BMCappelletti]

The measurements are in ohms? Not k ohms? Confirm if the meter face shows 'k' ohms. If in ohms, these parts are defective. Suggest to flux (carefully) and remove them for another measurement check while the parts are removed from the board. Share the measurements again.

Yes, ohms. Not k ohms.
Measurements pretty much the same from a donor board I have here. Although I have to ideia what is the issue with that one, cause I only bought it for parts.

[mon2]

Perhaps the measurements are being influenced by other parts on the board.

Disconnect the battery. Power up and measure the voltage to ground on:

F5200

What is the voltage? Is it stable?

[BMCappelletti]

Perhaps the measurements are being influenced by other parts on the board.

Disconnect the battery. Power up and measure the voltage to ground on:

F5200

What is the voltage? Is it stable?

Stable 12.3V.

[mon2]

Then the mosfets are ok as they are switching to buck / boost regulate the 20v or 5v input.

Remove all power. Meter in resistance mode. Test the resistance across the battery mosfet @ Q5265.

Same measurements.

[BMCappelletti]

Then the mosfets are ok as they are switching to buck / boost regulate the 20v or 5v input.

Remove all power. Meter in resistance mode. Test the resistance across the battery mosfet @ Q5265.

Same measurements.

So... pins 1 2 and 3 (PPVBAT_AON_CHGR_R)
to 4 (CHGR_BGATE) - 1.1 MOhms
to 5 (PPVBAT_AON_CONN) - 2.2 MOhms

Pin 4 to 5 - 0.94 MOhms

[mon2]

Looks ok.

Does your battery have a voltage at this time? Connect the battery. Connect the power adapter. What is the voltage to ground at the fuse F5200?

[BMCappelletti]

Looks ok.

Does your battery have a voltage at this time? Connect the battery. Connect the power adapter. What is the voltage to ground at the fuse F5200?

12.3V. As I have the board on the machine, for better connecting the battery, I measured on the same points from F5200, which are PPUS_AON (measured on FP800) and PPVBAT_AON_CHGR_REG, measured on C5258.

[mon2]

Connect the power adapter. What is the voltage to ground of CHGR_AUX_DET? Don't believe you have posted this measurement.

Disconnect the power adapter, what is the voltage @ F5200? This will be the power path from the battery only.

[BMCappelletti]

Connect the power adapter. What is the voltage to ground of CHGR_AUX_DET? Don't believe you have posted this measurement.

Disconnect the power adapter, what is the voltage @ F5200? This will be the power path from the battery only.

5V on CHGR_AUX_DET, measured on R5215 and R5216. R5215 has 20V on the other side. R5216 nothing on the other side. With and without battery.
F5200 is 12.3V with power adapter and goes down when disconnecting power. If testing the same with the battery connected, it is 12.3V and changes to 8.4V for a second, before going down.

[mon2]

Remove all power. Meter in resistance mode.

What is the resistance across C5260? This is to measure the full path resistance of the battery charge leg of the circuit.

[BMCappelletti]

Remove all power. Meter in resistance mode.

What is the resistance across C5260? This is to measure the full path resistance of the battery charge leg of the circuit.

1.2 ohms accross that cap.
But... check these pictures. Two are from the board I am working on. The third is from a donor board.

[mon2]

The top side is chipped but check is you have at least 12v3 at the fuse. If yes, for now, ignore.

From your linked wiki…

~ 12.28-12.35 = Possibly normal, however may indicate a communication issue between the SOC and one of the PMICs or between the SOC and other components as well as corrupt firmware.

Try a DFU.