Macbook Air 2020 A2179 820-01958 battery problem?

[sdogs]

Hi everyone,
I have a MacBook Air A2179 in my hands that had power problems (5V to the USB-C port intermittently).
After a first inspection I could see that the D3302 protection IC was burnt out, so I replaced it but the problem was not solved, it seems like intermittent 5v input.
I then replaced the two u3200s (CD3217B12ACE) and now I have stable 20 volts and the macbook has turned back on.
Unfortunately I have a further problem, it works very slowly and the fan runs at maximum and if I disconnect the charger it turns off, it's as if the battery was disconnected.
I measured the voltage at the battery connector (j6950) and I have 12v at pin 1 and 2 (PPVBAT_G3H_CONN), 3.3V at pin 3 and 4 (SMBUS 3V3_BATT_SCL E SDA) and 0v at pin 5 (SYS_DETECT_L)
Maybe the battery is dead? Did it discharge too much?
I've done some other checks and everything seems normal, or am I doing something wrong?

[mon2]

If you have a slow CPU and high fan speed, you have a sensor fault. The sensor faults are often linked to a non-working I2C / SMBUS line. These are party lines where multiple slave devices are addressed by unique addresses inside each sensor. If anyone pulls down the line, the entire network of devices will fail to operate. Locate each I2C / SMBUS on the board and verify their voltage to ground for each SCL / SDA line. If this is not practical, remove all power (no battery) and check each SCL / SDA line using DIODE mode on your meter.

Red meter probe to ground; black meter probe to the I2C line to test. Do also review again the ESD protected battery lines but with out the battery using diode mode. The trackpad features some of these sensors as well.

[sdogs]

when I received the macbook it didn't charge but it worked normally only with the remaining battery charge. I waited for the components to arrive which I then replaced and now it has this problem. If the sensors had been faulty he would have had the same problem, could it be the battery that stopped working?

[mon2]

Try a PRAM reset since the battery area was the region of repair. Your SMBUS lines for the battery are ok if at 3v3 for each SCL and SDA line.

MacBook Air SMC and PRAM reset - Apple Community

[sdogs]

unfortunately the SMC reset did not give the results I was hoping for, today I should receive a new battery to test, I hope it works.
The only thing that I didn't understand well and would like to understand, the SYS_DETECT_L signal should be the communication between battery and logic, is this correct?

[mon2]

No. This is just an active low (since suffix is _L) signal to inform to the charger IC that a battery is present.

The communication is over the 2 smbus (i2c) lines which are scl and sda.

[sdogs]

Thank you so much for your help, you help me understand and I am very grateful ;-)
Am I referring to this part of the diagram?

[mon2]

The posted schematic is just one network of i2c pins. This segment swings to 1v8. There are others onboard. Confirm that each is operational. You can confirm by checking the voltage of each scl and sda line or by removing all power and check the same lines in diode mode. Red meter probe to ground. Black to the pin to test.

The track pad has a few sensors so be sure the cable is properly seated. If a sensor is not detected, the fan spin will be high and the cpu will be throttled.

[sdogs]

Thanks Mon2, your help is always precious ;-)
Yesterday I tried a new, non-original but good quality battery and the MacBook works!!!
The problem related to the sensors seemed strange to me, when they entrusted it to me it only worked on battery power.
In summary, I replaced both U3200 and D3302 and the logic was resurrected!!!