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SPN 3216 FMI 10

Aftertreatment 1 Intake NOx — Abnormal rate of change.
The value is changing faster than is physically believable.

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

What FMI 10 usually points to: Intermittent wiring, a sensor glitch, or a sudden real event such as a burst hose. More on FMI 10.

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 10 mean?

Aftertreatment 1 Intake NOx — abnormal rate of change. The value is changing faster than is physically believable.

Is SPN 3216 FMI 10 serious?

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

What should I check first for SPN 3216 FMI 10?

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