What causes a U3345 code?

U3345 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 U3345 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with U3345 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

U3345

Manufacturer-specific network code U3345

What it means

Internal ECU communication fault where the primary processor cannot talk to the secondary safety processor. Usually indicates hardware failure.