Iveco 259 – EDC (Electronic Diesel Control): Short-circuit on-board network control circuit pump

The engine's computer has detected a short circuit to the positive voltage (the on-board network, which is typically 12V or 24V depending on the truck) within the electrical circuit that controls the fuel pump or the fuel pump relay.

• Iveco Daily
• Iveco Stralis
• Iveco Eurocargo
• Iveco Tector

1. 1

   Check the Fuel Pump Relay: Locate the fuel pump relay in the main distribution fuse box (often designated as relay T08 or T10, depending on the model year). A fused or internally shorted relay coil is a common cause of this code.

2. 2

   Inspect the Wiring Harness: Trace the wiring from the EDC to the fuel pump relay, and from the relay to the fuel pump. Look for chafed insulation, pinched wires, or melted harness sections that could be shorting directly to a 12V/24V power source.

3. 3

   Check the Fuel Pump Control Unit: On models equipped with a dedicated fuel pump control module, inspect the module's connector for water ingress, corrosion, or burnt pins.

4. 4

   Test the Fuel Pump: Disconnect the fuel pump and check the internal resistance of the pump motor using a multimeter. A dead short inside the pump motor can cause the control circuit to overload.

5. 5

   Check Associated Fuses: Inspect the main fuse box for blown fuses related to the fuel pump (such as F08 or F12). If a fuse blows immediately upon turning the ignition on, you have a hard short to ground or power.

1. 1

   Disconnect Power

   Disconnect the negative battery terminal to prevent any further electrical damage while working on the circuit.

2. 2

   Relay Replacement

   If the diagnostic tests point to a faulty relay, pull the old relay from the fuse box. Clean the socket terminals with electrical contact cleaner to ensure there is no residual melting or corrosion, and install the new relay.

3. 3

   Wiring Repair

   If a short is found in the harness, cut out the damaged section of the wire. Solder in a new section of automotive-grade wire of the same gauge and seal it with heat-shrink tubing to protect it from moisture and future chafing.

4. 4

   Module/Pump Replacement

   If the fuel pump control unit or the fuel pump itself is internally shorted, unbolt the faulty component, disconnect the harness, and install the replacement part.

5. 5

   Clear Codes

   Reconnect the battery. Connect an Iveco EASY diagnostic tool (or a compatible heavy-duty OBD scanner) to the vehicle's diagnostic port and clear the 0259 fault code.

6. 6

   Verify Repair

   Turn the ignition to the "ON" position and listen for the fuel pump to prime. Start the engine and monitor the diagnostic tool to ensure the code does not return.