Case IH F-175-01 - ECU – ECU: Oil temperature sensor voltage is lower than expected

The Engine Control Module (ECM/ECU) is receiving a signal voltage from the Engine Oil Temperature Sensor that is below the minimum acceptable threshold (typically below 0.2 VDC), indicating a short to low source or ground.

• MAGNUM AFS Connect
• Magnum series (235-340, 7110)
• Steiger series (350-600)
• Puma CVX
• Maxxum series (MX100, MX110, MX120, MX135, MXM120, MXM130)
• Farmall models
• Axial-Flow 240 series
• 5130 Harvester
• 8800 Harvester

1. 1

   Visually inspect the engine oil temperature sensor and its electrical connector for physical damage, corrosion, or bent pins

2. 2

   Trace the wiring harness from the sensor back to the ECU, looking for chafed wires, bare spots, or pinched areas causing a short to ground

3. 3

   Disconnect the sensor, turn ignition ON (Engine OFF), and use a multimeter to verify the ECU is supplying a 5-volt reference signal to the connector

4. 4

   Measure the resistance across the sensor's terminals and compare to OEM specifications to check for an internal open circuit or dead short

5. 5

   Verify overall battery and charging system voltage on the instrument cluster (low system voltage below 11.5V can cause erroneous sensor codes)

1. 1

   Preparation

   Park the machine on a level surface, turn off the engine, and disconnect the negative battery cable to prevent electrical shorts.

2. 2

   Locate the Sensor

   Locate the engine oil temperature sensor, which is typically threaded into the engine block near the oil filter housing or oil cooler module.

3. 3

   Disconnect

   Depress the locking tab on the electrical connector and carefully unplug the harness from the sensor.

4. 4

   Removal

   Place a small drain pan under the sensor area to catch any residual oil. Use a deep socket or wrench to unthread and remove the faulty sensor.

5. 5

   Installation

   Thread the new OEM sensor into the port by hand to prevent cross-threading. Tighten to the manufacturer's specified torque (do not overtighten, as these are often brass fittings).

6. 6

   Reassembly

   Reconnect the electrical harness, ensuring it clicks securely into place. Reconnect the battery.

7. 7

   Clear and Verify

   Turn the key ON and use a diagnostic scan tool (or the in-cab display) to clear the inactive fault code. Start the engine, check the sensor area for oil leaks, and allow the machine to reach operating temperature to verify the code does not return.