Massey Ferguson 94 – ECU: High Fuel Filter Pressure Sensor Fault

The Engine Control Unit (ECU) has detected a voltage from the fuel filter pressure sensor that is higher than the maximum expected value, or the signal circuit is broken (open circuit). An open circuit suggests a break in the wiring or a disconnected plug, while a voltage above normal typically points to a short circuit to a power source or an internal failure of the sensor itself.

• 4600 Series
• 4600M
• 4700 Series
• 5400 Series
• 5465
• 5470
• 5475
• 5480
• 5600 Series
• 5700 Series
• 6400 Series
• 6460
• 6465
• 6475
• 6480
• 6485
• 6490
• 6495
• 6497
• 6499
• 7400 Series
• 7465
• 7475
• 7485
• 7490
• 7495
• 7497
• 7499
• 7600 Series
• 7614
• 7615
• 8400 Series
• 8450
• 8460
• 8470
• 8480
• 8600 Series
• 8650
• 8660
• 8670
• 8680
• 8690

1. 1

   Visually inspect the fuel filter pressure sensor (3-wire sensor typically mounted on the fuel filter head or low-pressure line) and its electrical connector for dirt, moisture, or corrosion.

2. 2

   Inspect the wiring harness leading to the sensor for chafing, pinching, or breaks, paying close attention to areas where it may rub against the frame or engine components.

3. 3

   Test the 5V reference voltage (Key ON, Engine OFF): Disconnect the sensor and probe the 5V reference wire in the harness connector to a known good ground. It should read approximately 5.0 volts.

4. 4

   Test the ground circuit: Probe the ground terminal in the harness connector to the battery negative. Resistance should be less than 1 Ohm.

5. 5

   Test for a short to power: With the sensor disconnected, probe the signal wire terminal to ground. It should read 0 volts.

6. 6

   Perform a sensor signal test (if harness tests OK): Reconnect the sensor and back-probe the signal wire (Key ON, Engine OFF). Voltage should be around 0.5 volts. A reading near 5.0 volts indicates an internal short within the sensor.

1. 1

   Resolve electrical issues

   If diagnostic checks reveal a wiring problem (missing 5V reference, bad ground, or short circuit), repair the wiring harness by fixing broken wires, cleaning corroded connectors, or re-routing chafed sections.

2. 2

   Replace fuel filter pressure sensor

   If wiring and ECU outputs are correct, the sensor itself is faulty. Relieve fuel system pressure (have a rag ready to catch minor fuel spillage), unplug the connector, use an appropriate wrench to unscrew the old sensor, ensure the sealing surface is clean, install the new sensor to manufacturer specifications (do not overtighten), and reconnect.

3. 3

   Clear fault codes

   Start the tractor and use the dash interface or a diagnostic tool to clear the fault codes.

4. 4

   Verify the repair

   Let the engine run and verify that the fault code does not reappear.