What causes a U3099 code?

U3099 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 U3099 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with U3099 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

Log in Sign up

OBD-II

U3099

Manufacturer-specific network code U3099

What it means

Loss of communication with the ignition switch or passive entry module. The vehicle cannot authenticate the key presence.

Sign in to view symptoms, probable causes, diagnostic steps, severity, and related codes

Log in Sign up free