New Holland ENG 1012 – Engine Control Unit (ECU): Battery 5 V Reference 2 Circuit Low

The Engine Control Unit (ECU) outputs a steady 5-volt reference signal to power a specific group of engine sensors. The "Circuit Low" designation means the voltage on the #2 reference circuit has dropped below the acceptable operating threshold. This is almost always caused by a short to ground in the engine wiring harness or an internally shorted sensor that is pulling the circuit voltage down.

• L220
• L318
• SR175
• 200 Series loaders
• Alpha Series loaders
• TR Series track loaders
• TV Series track loaders

1. 1

   Perform a sensor isolation test by disconnecting sensors on the Reference 2 circuit one at a time to see if the 5V reference voltage returns to normal.

2. 2

   Inspect the engine wiring harness for chafing, pinched wires, or melted insulation, particularly where the harness routes around the engine block or metal brackets.

3. 3

   Disconnect the harness at the Engine ECU and check the pins for corrosion, moisture, or bent terminals, then measure the 5V output directly at the ECU pin to verify if the ECU itself has failed.

1. 1

   Power Down

   Turn off the machine and disconnect the negative battery cable before unplugging the ECU or major harness connections.

2. 2

   Locate the Short

   Use a digital multimeter (DMM) to measure the voltage at the 5V supply pin on one of the affected sensor connectors (Key ON, Engine OFF).

3. 3

   Isolate

   Unplug sensors on the Reference 2 circuit one by one.

4. 4

   Repair Wiring

   If the harness is shorted to ground, open the wire loom, locate the chafed wire, splice in a new section of wire using weather-sealed heat shrink connectors, and re-loom the harness. Ensure it is zip-tied away from vibration points.

5. 5

   Replace Sensor

   If a sensor is found to be shorted, remove it, clean the mounting port, and install the replacement sensor to OEM torque specs.

6. 6

   Clear Codes

   Reconnect all components and the battery. Use the New Holland Electronic Service Tool (EST) or a compatible diagnostic scanner to clear the inactive ENG 1012 code.

7. 7

   Verify

   Start the machine and verify that the check engine light remains off and the 5V circuit maintains proper voltage under vibration.