New Holland ENG 3166 – Engine Control Unit (ECU): Fuel Filter Heater Relay - Short Circuit to Battery

The Engine Control Unit (ECU) provides a signal to actuate the fuel filter heating relay control circuit, but it has detected that the power stage of this circuit is shorted to a high voltage source (battery voltage).

• T5.95
• T5.105
• T5.115
• T6 Series
• T7.220
• T7.235
• T7.250
• T7.260
• T7.270
• T8 Series
• CR9090
• CX8080
• CX8090
• Magnum Series (235 - 340 Series 4)

1. 1

   Verify the fault is currently active via the diagnostic display.

2. 2

   Inspect the wiring harness between the ECU and the fuel filter heater relay for chafed wires, melted insulation, or pinched areas that could cause a short to a 12V battery source.

3. 3

   Remove the fuel filter heater relay and test it for internal shorts using a multimeter.

4. 4

   Inspect the ECU connectors and pins for corrosion, moisture, or bent pins that could be bridging the circuit to a power pin.

1. 1

   Disconnect Power

   Disconnect the machine's battery to ensure safety while working on the electrical system.

2. 2

   Locate the Relay

   Refer to your specific model's fuse and relay panel diagram to locate the Fuel Filter Heater Relay.

3. 3

   Test the Circuit

   With the relay removed, use a digital multimeter to check for continuity to battery voltage on the ECU control wire socket. If voltage is present when it shouldn't be, the wiring harness is shorted and must be traced and repaired.

4. 4

   Replace the Relay

   If the wiring harness tests fine and shows no shorts to battery, the relay itself has failed internally. Replace the relay with a new OEM unit.

5. 5

   ECU Verification

   In rare cases where both the wiring and relay are functional, the ECU's internal power stage may be faulty, requiring ECU replacement or repair.

6. 6

   Clear Codes

   Reconnect the battery, turn the ignition on, and use a CNH Electronic Service Tool (EST) or the in-cab diagnostic menu to clear the ENG 3166 fault code. Run the engine to verify the code does not return.