Case IH 3304 – Engine Control Unit (ECU / EDC - Electronic Diesel Control): Cylinder 4 Specific Errors - Signal Low

The engine control module has detected an abnormally low electrical signal or a lack of expected mechanical response from the fuel injector on Cylinder 4. This is typically caused by an open circuit, a short to ground in the injector wiring harness, high resistance in the connections, or a failed injector solenoid coil.

• Magnum 235
• Magnum 260
• Magnum 290
• Magnum 315
• Magnum 340 (Series 4)
• Steiger Series
• Puma Series
• Case Construction Equipment

1. 1

   Harness Inspection: Visually inspect the engine wiring harness from the Engine ECU to the Cylinder 4 injector. Look for chafed wires, melted insulation, or pinch points that could cause a short to ground (low side to battery/ground).

2. 2

   Connector Check: Disconnect the harness at the Cylinder 4 injector and at the ECU. Inspect the pins for corrosion, moisture, or bent terminals.

3. 3

   Resistance Test (Ohm Test): Using a digital multimeter, measure the resistance across the terminals of the Cylinder 4 injector solenoid. Compare the reading to the OEM specification (typically less than a few ohms). An infinite reading (OL) indicates an open internal coil, while a reading of 0 indicates a dead short.

4. 4

   Continuity Test: Check for continuity on both the supply and return wires between the ECU connector and the injector connector to rule out a broken wire.

1. 1

   Disconnect Power

   Turn off the machine and disconnect the negative battery cable to prevent electrical spikes.

2. 2

   Gain Access

   Remove the engine covers or valve cover as necessary to access the fuel injectors (procedure varies depending on the specific FPT engine model, e.g., 6.7L vs. 8.7L).

3. 3

   Repair Wiring (If Applicable)

   If the diagnostic checks revealed a broken or shorted wire, repair the harness using OEM-approved weatherproof splices, or replace the injector wiring harness section.

4. 4

   Replace Injector (If Applicable)

   If the injector solenoid failed the resistance test: Clean the area around the Cylinder 4 injector to prevent debris from entering the cylinder. Disconnect the high-pressure fuel line and the electrical connector. Remove the injector hold-down clamp and carefully extract the injector. Install the new injector with new O-rings and copper sealing washers. Torque the hold-down clamp and fuel lines to OEM specifications.

5. 5

   Reassembly & Calibration

   Reconnect the battery. If a new injector was installed, use the CNH Electronic Service Tool (EST) to input the new injector's trim code (IQA code) into the Engine ECU so it can properly fuel the cylinder.

6. 6

   Clear Codes

   Clear the inactive 3304 fault code and test run the engine to verify the repair.