Case IH 3148 – Engine Control Unit (ECU) / EDC: Coolant Temperature Sensor Dynamic Test - Failure (Minimum Temperature Raise Not Reached)

The Engine Control Unit (ECU) continuously monitors the engine coolant temperature during operation. This fault code is triggered when the ECU runs a dynamic test and detects that the engine coolant temperature has failed to increase by the minimum expected amount within a specified time limit, indicating either a stuck-open engine thermostat or a faulty coolant temperature sensor.

• Magnum series (180, 200, 220, 240, 235-340 Series 4)
• Steiger series (350-600)
• Puma
• Maxxum
• Optum
• Luxxum
• Axial-Flow series (AFX8010)

1. 1

   Check engine coolant level in the expansion tank or radiator to ensure it is at the proper level, as low coolant can prevent accurate sensor readings.

2. 2

   Inspect the wiring harness and electrical connector at the coolant temperature sensor for corrosion, chafing, or loose pins.

3. 3

   Verify actual engine temperature (stuck-open thermostat cause): Connect a diagnostic scan tool to monitor live data and use an infrared laser thermometer on the thermostat housing. If the actual temperature is low and matches the scan tool, the engine is overcooling.

4. 4

   Verify sensor accuracy (faulty sensor cause): If the actual engine temperature is rising normally but the scan tool reading remains low or stagnant, test the sensor's resistance across its pins with a multimeter and compare to OEM specifications.

1. 1

   Prepare machine for sensor replacement

   If replacing a faulty Coolant Temperature Sensor: Park the machine on a level surface, turn off the engine, and allow it to cool completely. Disconnect the battery.

2. 2

   Drain coolant

   Partially drain the engine coolant to a level just below the sensor port to prevent fluid loss.

3. 3

   Remove faulty sensor

   Disconnect the electrical wiring harness from the coolant temperature sensor. Use a deep socket or wrench to unscrew the faulty sensor from the engine block or thermostat housing.

4. 4

   Install new sensor

   Apply a liquid thread sealant or Teflon tape to the threads of the new sensor (if it does not come with pre-applied sealant). Thread the new sensor into the housing and tighten to the manufacturer's torque specification. Reconnect the electrical harness.

5. 5

   Remove thermostat housing

   If replacing a stuck-open Thermostat: With the coolant partially drained, loosen the hose clamps and remove the upper radiator hose from the thermostat housing. Remove the bolts securing the thermostat housing to the engine block.

6. 6

   Remove old thermostat

   Remove the old thermostat and scrape away any old gasket material from the mating surfaces.

7. 7

   Install new thermostat

   Install the new thermostat (ensure the jiggle valve/bleed hole is positioned correctly, usually at the top) and a new gasket. Reinstall the housing and torque the bolts to spec. Reattach the radiator hose.

8. 8

   Refill and bleed cooling system

   Final Steps: Refill the cooling system with the correct CNH-approved coolant. Reconnect the battery, start the engine, and let it idle with the radiator cap off to bleed any trapped air from the cooling system.

9. 9

   Clear code and verify repair

   Use a diagnostic tool to clear fault code 3148. Run the machine under load to ensure it reaches operating temperature and verify the code does not return.