What causes a SPN 2959 code?

SPN 2959 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 2959 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 2959 active.

How do I fix SPN 2959?

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 2959

J1939 SPN 2959 — Aftertreatment/Emissions parameter

What it means

Aftertreatment 1 Intake Gas Sensor Power Supply Circuit - Voltage Below Normal or Shorted to Low Source. This code identifies an electrical issue with the power supply specifically to the upstream (intake) NOx sensor.