Case IH F-153-21 - ECU – Engine Control Unit (ECU): Crankcase pressure too low

The physical signal from the crankcase differential pressure sensor has drifted below the lower acceptable limit, indicating an implausibly low pressure value. This is typically caused by a faulty sensor, a defect in the wiring (short circuit to ground or open circuit), or a mechanical issue such as the engine blow-by valve being locked in the open position.

• MAGNUM AFS Connect
• 240 Series Axial-Flow Combines (5140, 6140, 6150, 7140, 7150, 7240, 7250, 8240, 8250, 9240, 9250)
• Steiger
• Magnum
• Puma

1. 1

   Verify Active Status: Use an Electronic Service Tool (EST) to verify if the fault code is currently present and active.

2. 2

   Wiring and Connector Inspection: Check the wiring harness leading to the crankcase pressure sensor for breaks, chafing, or loose connections. Look for a short circuit to the battery negative terminal or an open ground line.

3. 3

   Sensor Accuracy Check: Check the physical range of the crankcase pressure sensor voltage with a multimeter. If the voltage is below the lower limit value at key-on/engine-off, the sensor is likely defective.

4. 4

   Mechanical Inspection: Inspect the crankcase ventilation system and blow-by valve to ensure the valve is not mechanically stuck in the open position, which can cause an actual low-pressure condition.

1. 1

   Preparation

   Turn off the machine, remove the key, and allow the engine to cool. Ensure the battery disconnect switch is turned off.

2. 2

   Locate the Sensor

   Locate the crankcase pressure sensor on the engine block/crankcase breather assembly.

3. 3

   Disconnect Wiring

   Carefully unplug the 3-pin electrical connector from the sensor.

4. 4

   Remove the Sensor

   Unthread or unbolt the defective crankcase pressure sensor from its mounting port.

5. 5

   Install the New Sensor

   Install the replacement sensor (ensure any required O-rings are seated properly) and tighten to OEM torque specifications.

6. 6

   Reconnect

   Plug the 3-pin wiring harness back into the new sensor, ensuring the locking tab clicks into place.

7. 7

   Clear Codes

   Reconnect the battery, turn the ignition on, and use your diagnostic scanner/EST to clear the F-153-21 fault code.

8. 8

   Test Run

   Start the engine and monitor the crankcase pressure data on the diagnostic tool to ensure it is reading within the normal physical range and the code does not return.