What causes a SPN 3227 code?

SPN 3227 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 3227 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 3227 active.

How do I fix SPN 3227?

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 3227

SPN 3227 - Aftertreatment 1 Intake NOx Sensor Power Supply

What it means

This code indicates an electrical circuit fault specifically related to the power supply or internal heater circuit of the Inlet (Upstream) NOx sensor.