Diag Mode (Diagnostic Mode) is a special function hidden inside most smartphones.
Brand / Model Code / Steps Extra Info
Huawei ##2846579## → Project Menu > Background Settings > Manufacture Open port via HCU or OptuPlus
Vivo *#585#, *#588#, ##558# → Quality Verification Test > Diagnostic Port Works on most Vivo models
Motorola Motorola Menu > Enable Diag [Factory Enabled] May require service menu access
OnePlus *#801#, *#8011# OR CDMA/LTE > Volte > OnePlus Open Diag Menu > Rndis, diag switch ON Works on OxygenOS & ColorOS builds
LT MobileSmartphone deals CDMA/LTE > Volte > LT Open Diag Menu Used for CDMA/LTE testing
China Mobile ##717717## Some models require engineering mode enabled
Samsung (Sprint) ##3424# Opens Sprint Diag Menu
Samsung (Verizon/USC) ##3666333# For Verizon & US Cellular models
Samsung (Others) *#0808# USB settings menu
Xiaomi / RedmiSmartphone deals ##717717##, ##13491## OR Enable Diag in engineering settings Works on MIUI-based devices
Lenovo ##8899## Opens Lenovo service mode
ZTE *#7678# OR Enable Hidden Menu: ZTEOPENEM# (983673636#) → Quick Pop-Up → 98387274# Also via CDMA/LTE > Volte > ZTE Open Diag Menu
LG Open Diag Menu OR *#546368#*model# OR ##7262626## Sprint & other variants supported
OPPO *#801# → Enable Engineer Mode Toggle Works on ColorOS
