Case IH 121 – ENG: Engine Position Sensor (8.3, 9 Liter) or Crankshaft Sensor (15 Liter) is failed.

The Engine Control Module (ECM) has detected a loss of signal from the crankshaft position sensor (also known as the engine speed/position sensor) while the engine was running.

• MX Magnum
• STX Steiger
• STX
• TR320
• Puma
• Maxxum

1. 1

   Verify the sensor supply circuit using a multimeter or test lamp to check for 5-VDC power and a solid ground at the sensor connector

2. 2

   Visually inspect the wiring harness from the sensor to the ECM for open circuits, short circuits, or broken wires

3. 3

   Check the crankshaft vibration damper for wear or failure, which can cause severe vibrations and signal loss at higher RPMs

4. 4

   Check the tone wheel on the crankshaft for looseness and inspect crank bearings for excessive play that could push the tone wheel out of range

1. 1

   Turn the keyswitch to the OFF position.

2. 2

   Locate the crankshaft position sensor.

   It is typically located on the intake side of the engine, near the flywheel housing or the front gear cover.

3. 3

   Disconnect the sensor wiring harness and inspect the connector pins.

   Check for corrosion or pushed-back pins.

4. 4

   Remove the retaining bolt and pull the old sensor out of the housing.

5. 5

   Install the new Engine Position / Crankshaft Sensor and secure the bolt.

6. 6

   Reconnect the wiring harness securely.

7. 7

   Validate the repair.

   Perform a key cycle, start the engine, and let it idle for 1 minute. The fault code status should change to INACTIVE, and the amber CHECK ENGINE lamp will turn off.

8. 8

   Clear the inactive code from the ECM memory.

   Use a recommended electronic service tool to issue a 'Reset All Faults' command.