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SPN 3216 FMI 12

Aftertreatment 1 Intake NOx — Bad intelligent device or component.
A smart sensor, actuator, or module has reported an internal failure or is not responding correctly.

What the SPN covers: NOx sensor reading in the exhaust before the SCR catalyst (engine-out NOx). More on SPN 3216.

What FMI 12 usually points to: Internal failure of the device itself; sometimes a power/ground problem makes a good device look bad. More on FMI 12.

Severity

MEDIUM — fix soon

Can lead to SCR efficiency codes and inducement derates if not repaired.

Likely causes

  1. Failed NOx sensor (common)
  2. Sensor not reaching operating temperature
  3. Exhaust leak near the sensor
  4. Network or power fault to the sensor module

Checks & fixes (easiest first)

  1. Check for exhaust leaks upstream of the sensor
  2. Check sensor power/ground and CAN wiring
  3. Compare inlet and outlet NOx readings
  4. Replace sensor per OEM test results

FAQ

What does SPN 3216 FMI 12 mean?

Aftertreatment 1 Intake NOx — bad intelligent device or component. A smart sensor, actuator, or module has reported an internal failure or is not responding correctly.

Is SPN 3216 FMI 12 serious?

Can lead to SCR efficiency codes and inducement derates if not repaired.

What should I check first for SPN 3216 FMI 12?

Check for exhaust leaks upstream of the sensor; Check sensor power/ground and CAN wiring; Compare inlet and outlet NOx readings.