Asus ZB551KL Training & Trouble Shouting Manual page 54

Sub MIC Abnormal (1)
• MIC_BIAS1_Sub without 1.8V
– Check L808, C820, U1001
Blow air flow to mic device,
MIC3_P_1/MIC3_M_1 no signal
- Check mic device and U800, L812, C819
• PMIC_AUDIO_REF_CLK no signal
– Check R410, U0501