Case IH 3509 – Engine Control Unit (ECU / EDC17 / EEM4) or Transmission Control Unit (TCU): Fuel tank below critical level / Sensor Supply 1 voltage out of range / Clutch pressure low

This code represents a conflation of conditions: SPN 96 FMI 1 indicates a critically low fuel tank risking air intrusion; SPN 3509 (Engine ECU) indicates Sensor Supply 1 voltage is out of range or shorted; SPN 3509 (Transmission TCU) indicates low clutch pressure due to wear, leaks, or a failing solenoid.

• Case IH Maxxum (5120-5150 series)
• Puma
• Magnum
• Optum
• Steiger (350 to 600 HP)
• Case IH combine harvesters (2166, 2388)

1. 1

   For the Fuel Level Condition: Visually verify the actual fuel level in the tank.

2. 2

   For the Fuel Level Condition: Check the fuel level sensor wiring harness for correct voltage supply and resistance.

3. 3

   For the Fuel Level Condition: Check the fuel lines for air intrusion.

4. 4

   For SPN 3509 (Sensor Supply 1 - Engine): Check the main battery voltage (must be above 11.5V).

5. 5

   For SPN 3509 (Sensor Supply 1 - Engine): Inspect the engine wiring harness for a short circuit to ground or a short circuit to the battery positive terminal.

6. 6

   For SPN 3509 (Sensor Supply 1 - Engine): Test the 5V reference supply at the connected sensors (e.g., Fuel Rail Pressure sensor pins).

7. 7

   For SPN 3509 (Clutch Pressure Low - Transmission): Check the transmission hydraulic fluid level and condition.

8. 8

   For SPN 3509 (Clutch Pressure Low - Transmission): Inspect the transmission circuit for external or internal hydraulic leaks.

9. 9

   For SPN 3509 (Clutch Pressure Low - Transmission): Test the transmission solenoid valve for proper operation.

1. 1

   Refill the fuel tank to the proper level.

   If resolving the Fuel Level / Air Contamination issue.

2. 2

   If the tank was run dry, bleed the fuel system to remove any air from the lines and filters before attempting to restart the engine.

   If resolving the Fuel Level / Air Contamination issue.

3. 3

   If the tank is full but the code persists, replace the faulty fuel level sensor.

   If resolving the Fuel Level / Air Contamination issue.

4. 4

   Disconnect the affected sensors (fuel rail pressure, oil pressure) one by one to see if a shorted sensor is pulling the 5V reference circuit down. Replace the sensor if it is internally shorted.

   If resolving SPN 3509 (Sensor Supply 1).

5. 5

   Repair any damaged, chafed, or melted sections of the engine wiring harness.

   If resolving SPN 3509 (Sensor Supply 1).

6. 6

   If the wiring and sensors are intact but the ECU is not outputting the 5V supply, the Engine Control Module (ECM) has an internal fault and must be replaced.

   If resolving SPN 3509 (Sensor Supply 1).

7. 7

   Replace the transmission oil filter if it is clogged.

   If resolving SPN 3509 (Clutch Pressure Low).

8. 8

   Replace the failing transmission solenoid valve or transmission pressure sensor if it is providing erratic readings.

   If resolving SPN 3509 (Clutch Pressure Low).

9. 9

   If hydraulic pressure is verified to be mechanically low, the transmission clutch pack must be rebuilt due to excessive wear.

   If resolving SPN 3509 (Clutch Pressure Low).