What causes a U0440 code?

U0440 can be triggered by several issues — see the verified probable causes and step-by-step diagnostics shared by mechanics and owners on OBDIY.

Can I drive with a U0440 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with U0440 active.

Follow the step-by-step diagnostic on this page, then read the verified fixes contributed by other Heavy Truck owners — the answer marked "Verified Cause" worked for the original poster.

OBDIY

OBD-II

U0440

Network/CAN bus communication code U0440

What it means

Invalid data received from the Gateway A module. The central gateway translates data between various CAN networks and is reporting invalid information flow.