SPN 107 FMI 3 – Air Filter Sensor failed high Fault Code (Symptoms, Causes & Fix)
The SPN 107 FMI 3 fault code is a diesel engine diagnostic trouble code indicating that the air filter sensor has failed high. This means the Engine Control Module (ECM) is receiving a signal from the air filter restriction sensor that is higher than expected, suggesting a potential issue with the sensor or its circuit.
What SPN 107 FMI 3 Means
SPN 107 FMI 3 represents a high signal from the air filter restriction sensor. This sensor monitors the air filter's condition by measuring the pressure difference across it. A high signal typically indicates that the sensor is detecting excessive restriction, which could be due to a faulty sensor, wiring issues, or an actual blockage in the air filter.
Common Causes of This Fault Code
- Failed sensor
- Wiring harness damage
- Connector corrosion
- ECM signal problems
- Voltage reference faults
Symptoms Drivers May Notice
When the SPN 107 FMI 3 fault code is active, drivers might notice a reduction in engine performance due to restricted airflow. The engine may also enter a derate mode to protect itself from potential damage. Additionally, a check engine light may illuminate on the dashboard.
How Technicians Diagnose This Fault
Technicians begin diagnosing this fault with a visual inspection of the air filter to check for excessive dirt or blockage. If the filter is clean, the next step is to inspect the wiring harness and connectors for any signs of damage, corrosion, or loose connections. Using a multimeter, technicians will verify the proper voltage and ground at the sensor connector. They will also perform a continuity test on the wiring from the sensor to the ECM to check for open circuits. If all wiring and connections are intact, the sensor itself may be faulty and require replacement.
Common Misdiagnosis
Common mistakes include assuming the air filter is the only issue without checking the sensor and wiring, replacing the ECM without verifying sensor and wiring integrity, and overlooking connector corrosion or pin damage.
Can You Keep Driving?
While it may be possible to continue driving with this fault code active, it is not advisable. The engine may enter a derate mode, reducing power and efficiency. Prolonged driving with restricted airflow can lead to further engine issues, so addressing the fault promptly is recommended.
Mechanic's Diagnostic Tip
Always verify the integrity of the wiring and connectors before replacing the air filter restriction sensor. Many issues stem from poor connections or damaged wiring rather than the sensor itself.
Frequently Asked Questions
What does SPN 107 FMI 3 indicate? It indicates a high signal from the air filter restriction sensor, suggesting a potential issue with the sensor or airflow restriction.
Can a dirty air filter cause this fault code? Yes, a dirty or blocked air filter can cause the sensor to read high, triggering the fault code.
Is it safe to drive with this fault code? While you may be able to drive, it is not recommended as it can lead to reduced engine performance and potential damage.
