SPN 3216 FMI 20 Fault Code [Explained]

SPN 3216 engine fault code indicates after treatment 2 intake NOx problem. A FMI 20 means data drifted high as shown in data table:

SPN, FMI – Fault Code Meanings:

  • 3216, 2 – data erratic
  • 3216, 4 – low voltage or shorted
  • 3216, 9 – abnormal update rate
  • 3216, 10 – abnormal rate of change
  • 3216, 13 – out of calibration
  • 3216, 16 – above operating range
  • 3216, 20 – data drifted high


Suggested Fix:
The inlet NOx sensor is a device that connects to the ECM. You can replace it, or recalibrate the ECM.

I recently experienced an issue with my car where the check engine light came on and the performance of the vehicle was noticeably affected. After taking it to a mechanic, I was informed that the problem was a bad inlet NOx sensor. At first, I had no idea what that meant or how it could cause such a significant problem.

For those who may be unfamiliar, the NOx sensor is responsible for monitoring the levels of nitrogen oxide in the exhaust system of a vehicle. If it detects that the levels are too high, it sends a signal to the engine control module to adjust the fuel-to-air ratio to reduce emissions. A bad sensor can cause inaccurate readings, leading to decreased fuel efficiency, reduced performance, and potentially even damage to the engine.

In my case, the bad inlet NOx sensor was causing the engine to run too rich, resulting in decreased power and poor gas mileage. While it may seem like a minor issue, it can have a significant impact on the overall health and performance of a vehicle. It’s important to address any check engine light warnings promptly and have a trusted mechanic diagnose and repair the issue to prevent further damage.