What causes a SPN 3259 code?

SPN 3259 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 3259 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 3259 active.

How do I fix SPN 3259?

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 3259

SPN 3259 - Aftertreatment 1 Intake Oxygen Sensor High Voltage

What it means

Indicates that the Diesel Oxidation Catalyst (DOC) intake oxygen sensor circuit voltage is above the normal operating range, typically signaling a short to power or a failed internal sensor element.