SPN 3226 FMI 6: NOx Sensor Outlet - Current Above Normal or Grounded Circuit

Code identity

SPN

3226

FMI

6

System

scr

Vehicle classes

truck,bus,agricultural,construction,marine,industrial

Measurement and isolation sequence

1. Verify power and ground under load.
2. Compare connector voltage/current with controller-side values.
3. Isolate open, short-to-ground or short-to-high conditions.
4. Repeat the measurement under load after repair.

Misdiagnosis trap

Do not read an SPN/FMI combination as a failed-part label. Network messages, electrical circuits, sensors/actuators and mechanical systems can trigger the same family from different root causes. On heavy-duty equipment, derate or protection behaviour may be a secondary result.

SPN/FMI evidence chain

1. Confirm the SPN parameter and source ECU address.
2. Interpret the FMI fault mode separately.
3. Measure CAN physical layer and power supply.
4. Compare live message data with independent physical measurement.
5. If derate is present, retest under load after root-cause repair.

Related centers

Heavy trucks → · Tractors/agriculture → · Construction machinery →