Case IH 3165 – Engine Controller (Engine ECU / ENG): Fan Speed Sensor - Signal Low

This code indicates that the voltage signal coming from the fan speed sensor has dropped below the minimum acceptable threshold. This condition is typically caused by an open circuit, a short to ground in the sensor wiring, a failed sensor, or an improperly gapped sensor failing to read the fan rotor.

• Magnum 235 - 340 (Series 4)
• Steiger series
• 6140
• 7120
• 7230
• 8010
• T8.xxx Series

1. 1

   Visual Inspection: Inspect the fan speed sensor, its mounting bracket, and the target wheel/rotor for physical damage, heavy dirt, or debris buildup.

2. 2

   Wiring & Connector Check: Trace the wiring harness from the sensor back to the Engine ECU. Look for chafed wires, pinched lines, or corrosion inside the connector pins.

3. 3

   Circuit Testing: Use a multimeter to check for an open circuit or a short to ground on the sensor signal wire.

4. 4

   Sensor Gap Verification: Check the distance between the tip of the sensor and the fan rotor. If the sensor has backed out or the bracket is bent, the gap may be too large to generate a signal (standard gap is often around 1/8 inch depending on the specific fan assembly).

1. 1

   Power Down

   Turn off the machine, remove the key, and ensure no power is running to the fan. Apply safety locks if working inside a combine chassis.

2. 2

   Gain Access

   Open the cooler door or remove the protective fan cage/guards to access the fan impeller and sensor mounting bracket.

3. 3

   Disconnect

   Unplug the electrical wiring harness from the faulty fan speed sensor.

4. 4

   Remove

   Unthread the jam nuts securing the sensor and pull the old sensor out of the mounting bracket.

5. 5

   Install

   Thread the new OEM fan speed sensor into the bracket.

6. 6

   Set the Gap

   Adjust the sensor depth so that the gap between the sensor tip and the target wheel is set to the manufacturer's specification (approximately 1/8").

7. 7

   Secure

   Tighten the mounting nuts carefully. Do not overtighten, as these sensors are easily damaged.

8. 8

   Reassemble

   Reconnect the wiring harness and reinstall all fan cages and safety guards.

9. 9

   Test

   Start the machine, clear the inactive fault codes from the Engine ECU, and run the fan to verify that the RPMs hold steady and the code does not return.