What causes a U0861 code?

U0861 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 U0861 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with U0861 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

U0861

Network/CAN bus communication code U0861

What it means

Communication lost with Lighting Control Module 'H'. This code indicates an interruption in data exchange between the vehicle network and the specific lighting controller.