Case IH 3959 – Engine Control Module (ECM) / ISM-DI / EDC: ISM-DI Injector 2 And/Or 3 - Shorted To High Source

The engine control system has detected an abnormally high voltage on the control circuit for fuel injector 2 and/or 3. This is typically caused by the injector wiring harness shorting directly to a battery voltage source, or an internal short within the injector solenoid itself.

• skid steer
• Steiger tractors
• SSL (Skid Steer Loaders)
• CTL (Compact Track Loaders)

1. 1

   Visually inspect the engine wiring harness between the Engine Controller and Injectors 2 and 3. Look for chafed wires, melted insulation, or pinched areas that could cause the injector circuit to short to a 12V power source.

2. 2

   Disconnect the electrical connectors at Injector 2, Injector 3, and the Engine Controller. Use a digital multimeter to test the injector signal wires for a short to battery voltage.

3. 3

   Test the resistance of the solenoids on Injector 2 and Injector 3 to check for an internal short circuit.

4. 4

   Check for any other active fault codes, as multiple short-to-high codes may indicate a broader harness failure or a failed ECM.

1. 1

   Disconnect battery

   Disconnect the machine's battery before servicing the electrical system to prevent further damage to the ECM.

2. 2

   Repair or replace wiring harness

   If a short is found in the wiring during the diagnostic phase, repair the damaged section of the engine wiring harness or replace the harness entirely.

3. 3

   Replace fuel injector(s)

   If the wiring tests good but an injector fails the resistance test, replace the faulty fuel injector(s).

4. 4

   Replace Engine Controller

   If both the wiring harness and the injectors test perfectly but the fault persists, the official service documentation states to "Replace Engine Controller," as the internal COM2 output driver is likely burnt out or damaged.

5. 5

   Perform self-learning procedure

   After replacing the injectors or the Engine Controller, you must use a diagnostic service tool to perform the "Procedure To Restore Self Learning Parameters" (also known as injector coding/calibration).

6. 6

   Clear codes and verify

   Clear the fault codes, restart the engine, and verify that the code does not return.