MacBook Pro 820-01949 2020 with no internal display

[sekidata]

This A2251 MacBook Pro with mild liquid damage (USB-C area) is working fine on external display but does not recognize the internal LCD. I tried several displays and flex cables, and there is no backlight and no display. The internal does not show up in Settings>Displays, only the camera is recognized.

PP5V_S0SW_LCD is 0V except briefly during the chime (5.1V).
EDP_PANEL_PWR_EN is 0V except briefly during the chime (3.3V).
DP_INT_HPD is 0V except briefly during the chime (3.3V).

What would you check before blaming the EDP portion of the CPU?

 

[sekidata]

Just noticed that when the external display is unplugged, I do get steady values on PP5V_S0SW_LCD, EDP_PANEL_PWR_EN, DP_INT_HPD but no display whatsoever.

 

[2informaticos]

If DP_INT_HPD and 3V3/5V_S0SW_LCD stay high, then internal LCD is recognized by PCH.

You should check diode mode to ground on J8500 EDP data lines.

 

[sekidata]

EDP_INT_ML_P<1>: 8.1kΩ 0.29
EDP_INT_ML_P<2>: 1.6kΩ 0.28
EDP_INT_ML_P<3>: 1.6kΩ 0.29
EDP_INT_ML_N<1>: 7.8kΩ 0.29
EDP_INT_ML_N<2>: 1.6kΩ 0.28
EDP_INT_ML_N<3>: 1.5kΩ 0.29
EDP_INT_AUX_P: 27.8kΩ 0.28
EDP_INT_AUX_N: OL OL
I2C_TCON_SCL: 2.6MΩ 0.49
I2C_TCON_SDA: 2.7MΩ 0.48

I guess there are no shorts but the connection between EDP_INT_AUX_N and the CPU got severed somehow?

 

[2informaticos]

Possibly broken trace...

 

[sekidata]

Yeah, deep inside the board or the CPU... too bad.