Massey Ferguson U 1080 – Engine Control Unit (ECU) / Electronic Diesel Control (EDC): Sensor Supply Voltage 2

The 5-volt reference circuit (circuit #2) that powers a specific group of engine sensors is experiencing a voltage irregularity, indicating either a shortcut to battery positive (voltage is too high) or a shortcut to ground (voltage is too low).

• 8600 Series
• MF 8650
• MF 8660
• MF 8670
• MF 8680
• MF 8690

1. 1

   Check the tractor's main battery voltage to ensure it is sufficient and not overcharging.

2. 2

   Inspect the engine wiring harness for chafing, melting, or pinched wires looking for a physical short to ground or a short to battery positive.

3. 3

   Identify and isolate the sensors powered by the Supply Voltage 2 circuit to check for a dead short inside a single connected sensor.

4. 4

   Disconnect the sensors on this circuit and measure the voltage coming directly from the ECU pins for Sensor Supply 2 to verify if the ECU can output the correct 5V reference.

1. 1

   Disconnect Battery

   Always disconnect the negative battery terminal before unplugging the ECU or repairing wiring.

2. 2

   Unplug Sensors

   Disconnect the sensors on the Supply Voltage 2 circuit one by one. Reconnect the battery and cycle the key after each to see if the code changes from 'Active' to 'Inactive'. If unplugging a specific sensor clears the short, that sensor is internally shorted and must be replaced.

3. 3

   Repair Wiring

   If the sensors are fine, trace the wiring harness back to the ECU. Repair any damaged, corroded, or exposed wires using proper soldering and heat-shrink techniques, or replace the affected harness section.

4. 4

   Replace the ECU

   If the wiring harness tests perfectly for continuity and lacks any shorts, and the sensors are good, the internal power supply of the ECU has failed. Remove the ECU and install a replacement or reconditioned unit.

5. 5

   Clear Codes

   Reconnect all components, turn the ignition on, and use a diagnostic tool to clear the U 1080 fault code. Run the engine to verify the code does not return.