What causes a SPN 3231 code?

SPN 3231 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 3231 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 3231 active.

How do I fix SPN 3231?

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 3231

Aftertreatment 1 Intake NOx Sensor Heater Current Too Low

What it means

The Engine Control Module (ECM) has detected that the current draw for the NOx sensor heater circuit is lower than the expected threshold, usually indicating an open circuit.