Deutz-Fahr SPN 3480 FMI 3 – Aftertreatment Control Module (ACM) / Engine Control Unit (ECU): SCR Catalyst Temperature Sensor: Signal voltage too high

The controller has detected a voltage signal from the downstream SCR exhaust temperature sensor that exceeds the normal operating range. This condition is typically caused by a short to a high voltage source, an open circuit in the sensor's wiring, or an internal failure of the sensor itself.

• Deutz-Fahr Agrotron series
• Deutz-Fahr Serie 6
• Deutz-Fahr Serie 9

1. 1

   Inspect the wiring harness leading to the downstream SCR catalyst temperature sensor for chafing, melting, or corrosion at the connectors.

2. 2

   Disconnect the sensor, turn the ignition on (engine off), and use a multimeter to check the sensor signal circuit for a short to voltage condition (there should be no voltage on the ground pin).

3. 3

   Check for continuity between the sensor connector and the ACM/ECU connector to ensure there is no open circuit or shorted conductors in the harness.

4. 4

   If the wiring is completely intact and the sensor is replaced but the code remains, verify the ACM 2.1 module for an internal fault.

1. 1

   Power Down

   Turn off the ignition and wait for the vehicle's electrical system and the aftertreatment purge cycle to completely power down.

2. 2

   Locate the Sensor

   Locate the SCR downstream exhaust temperature sensor on the exhaust aftertreatment assembly (DOC/DPF/SCR unit).

3. 3

   Disconnect

   Carefully disconnect the electrical harness from the sensor.

4. 4

   Remove the Sensor

   Use the appropriate wrench to remove the temperature sensor from the exhaust pipe. Note: Exhaust sensors can be seized; applying penetrating oil beforehand is recommended.

5. 5

   Install New Sensor

   Thread the new OEM SCR temperature sensor into the exhaust bung and tighten to the manufacturer's torque specification.

6. 6

   Reconnect

   Reconnect the electrical harness, ensuring the connector clicks into place and is free of debris.

7. 7

   Clear Codes

   Connect a diagnostic tool (EST) to the machine, clear the SPN 3480 FMI 3 fault code, and run the engine to verify that the fault does not return and the sensor reads the exhaust temperature accurately.