Case IH 265 – Engine Control Unit (ECU / ECM): Fuel Temperature Sensor voltage is too low

The system detects low voltage at the fuel temperature sensor signal pin. The engine defaults to a predetermined value for fuel temperature, which can result in low engine power and a lack of protection for fuel temperature extremes.

• MX Magnum
• STX Steiger
• 2300 Series
• Steiger
• Magnum
• Puma
• Maxxum MX Series (MX80C, MX90C, MX100C)
• CX Series (CX50 to CX100)
• C Series (C50 to C90)

1. 1

   Verify system voltage by checking the battery, alternator, and alternator belt to ensure they are functioning correctly (low system voltage is a frequent cause of stored codes).

2. 2

   Inspect the engine harness and the connector at the fuel temperature sensor for moisture, dirt buildup, or extreme vibration damage.

3. 3

   Test the signal pin (e.g., pin 35 on the engine harness) with a multimeter to determine if the circuit is shorted to ground or has an open circuit causing the low voltage reading.

1. 1

   Power Down

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

2. 2

   Locate the Sensor

   Locate the fuel temperature sensor, which is typically mounted on the fuel filter housing or fuel pump manifold.

3. 3

   Inspect and Clean

   Disconnect the sensor harness. Inspect both the sensor pins and the harness connector for corrosion, bent pins, or pushed-back terminals. Clean with contact cleaner if necessary.

4. 4

   Test/Repair Wiring

   If the connector is clean, trace the wiring harness back to the Engine ECU. Repair any chafed wires that may be shorting to the engine block or chassis.

5. 5

   Replace the Sensor

   If the wiring harness tests good (providing the correct 5-volt reference) but the sensor is pulling the voltage low, the internal thermistor of the sensor has failed. Remove the old sensor and install a new OEM replacement.

6. 6

   Reassemble and Clear Codes

   Reconnect the harness and battery. Turn the key on to verify the code changes from "Active" to "Stored" or clears entirely. Run the engine to ensure full power is restored.