What does code U301B mean?

Q: What does code U301B mean?

Control Module Wake-up Circuit A Low. U301B indicates that a control module responsible for waking up other modules on the vehicle's communication network has detected a low voltage condition on the wake-up circuit it monitors. The module sets this code when the wake-up line, which is normally held at a defined voltage when inactive, drops below the expected threshold, suggesting a short to ground, an open circuit, or a failed module pulling the line low.

DTC codes / U30xx · Network wiring and bus faults / U301B

U301BControl Module Wake-up Circuit A Low

U301B indicates that a control module responsible for waking up other modules on the vehicle's communication network has detected a low voltage condition on the wake-up circuit it monitors. The module sets this code when the wake-up line, which is normally held at a defined voltage when inactive, drops below the expected threshold, suggesting a short to ground, an open circuit, or a failed module pulling the line low.

SystemNetwork

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyProfessional

AreaNetwork wiring and bus faults

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.