Deutz-Fahr SPN 3364 FMI 9 – Exhaust Aftertreatment Control Module (ACM 2.1) / Engine Management System (EMR4): NOx Sensor (Downstream SCR): Communication timeout on bus

The control unit has lost communication with the NOx sensor located downstream (after) the Selective Catalytic Reduction (SCR) catalyst. The controller is not receiving the expected data updates from the sensor over the CAN bus network.

• Deutz-Fahr Agrotron series
• Deutz-Fahr Serie 6 and Serie 9
• Deutz-Fahr 5090, 5100, 5110 C (LS/GS)
• Deutz-Fahr Virtus J (90, 100, 110, 120)

1. 1

   Check the wiring harness between the downstream NOx sensor and the ACM 2.1/EMR4 control unit for chafing, breaks, or melted wires.

2. 2

   Inspect the NOx sensor connector and the ECU pins for corrosion, moisture ingress, or bent pins.

3. 3

   Verify that the NOx sensor is receiving proper voltage and has a solid ground connection.

4. 4

   Test the CAN High and CAN Low communication lines at the sensor connector for proper resistance and voltage to ensure the bus is intact.

5. 5

   Check for an internal fault within the ACM 2.1 control unit itself, which can prevent it from processing sensor data.

1. 1

   Disconnect Power

   Turn off the machine and disconnect the battery to prevent electrical spikes.

2. 2

   Repair Wiring

   If the diagnostic checks revealed broken CAN lines or power wires, repair the harness and replace damaged connector pigtails.

3. 3

   Replace the Sensor

   If the wiring and CAN bus signals are verified as good, the downstream NOx sensor's internal module has likely failed. Remove the faulty NOx sensor from the exhaust piping downstream of the SCR catalyst and install the replacement.

4. 4

   ECU Repair/Replacement

   If a new sensor does not restore communication, the ACM 2.1 / EMR4 module will need to be removed and sent to a specialist (like Revonik) for internal repair, or replaced entirely.

5. 5

   Clear and Test

   Reconnect the battery, use a diagnostic tool (such as SerDia) to clear the SPN 3364 FMI 9 fault code, and run the engine to operating temperature to verify that the SCR system is functioning and the code does not return.