What causes a SPN 959 code?

SPN 959 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 SPN 959 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 959 active.

How do I fix SPN 959?

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

J1939 SPN

SPN 959

J1939 SPN 959 — Engine Management parameter

What it means

SPN 959 refers to the 'Seconds' component of the Engine Real-Time Clock (RTC). This is used by the Engine Management System to timestamp snapshots, fault codes, and maintenance intervals.