Case IH 3956 – Engine Controller / Engine Control Unit (ECU): Injector 1 And/Or 4 Shorted To High Source

The engine control system has detected a short circuit to a high voltage source (battery power) on the electrical circuit that controls fuel injector 1 and/or fuel injector 4.

• skid steer
• SR130
• SR160
• SR175
• SV185
• TR Series
• TV Series

1. 1

   Visually inspect the engine wiring harness running from the ISM-DI Engine Controller to Injectors 1 and 4. Look for chafed insulation, melted wires, or pinch points where the circuit could be shorting to a 12V power source.

2. 2

   Disconnect the electrical connectors at Injector 1 and Injector 4. Use a multimeter to measure the resistance across the injector coil pins to determine if the injector itself has failed and shorted internally.

3. 3

   Disconnect the harness at the Engine Controller and inspect the pins for corrosion, moisture intrusion, or damage that could cause a bridge/short between power pins and the injector driver pins.

1. 1

   Disconnect Power

   Disconnect the negative battery cable before servicing the fuel system or engine electronics.

2. 2

   Harness Repair

   If a short to power is located in the wiring harness during diagnostics, repair the damaged section of the wire using appropriate weather-sealed connectors, or replace the engine harness entirely.

3. 3

   Injector Replacement

   If Injector 1 or 4 failed the resistance test, remove the high-pressure fuel lines and replace the faulty injector(s). Note: When installing new injectors, the new injector calibration codes must be written to the ECU using the Electronic Service Tool (EST).

4. 4

   ECU Replacement

   If the wiring harness and injectors both test perfectly fine, the injector driver inside the Engine Controller has likely shorted out internally. Replace the Engine Controller.

5. 5

   Reprogramming

   If the ECU is replaced, use the EST diagnostic software to flash the correct engine datasets and restore self-learning parameters.