What does code U3503 mean?

Q: What does code U3503 mean?

Control Module Input Power A Circuit Intermittent/Erratic. U3503 is a generic network communication code indicating that a control module has detected an intermittent or erratic fault on its primary power supply circuit, typically the main battery feed. The module's internal diagnostics monitor voltage stability and set this code when power drops out or fluctuates beyond a calibrated threshold, often due to a loose connection, corroded terminal, or failing power relay.

DTC codes / U35xx · Network communication / U3503

U3503Control Module Input Power A Circuit Intermittent/Erratic

U3503 is a generic network communication code indicating that a control module has detected an intermittent or erratic fault on its primary power supply circuit, typically the main battery feed. The module's internal diagnostics monitor voltage stability and set this code when power drops out or fluctuates beyond a calibrated threshold, often due to a loose connection, corroded terminal, or failing power relay.

SystemNetwork

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaNetwork communication

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