What causes a SPN 3238 code?

SPN 3238 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 3238 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 3238 active.

How do I fix SPN 3238?

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 3238

Aftertreatment 1 Intake Gas NOx Sensor Power Signal Fault

What it means

This code indicates a fault in the heater power supply or signal circuit for the inlet NOx sensor, typically caused by a short or open circuit in the sensor wiring harness.