Case IH 3713 – Engine Control Unit (ECU) / EDC: Lambda sensor: Open Load error of the LSU Heater Power stage

The Engine Control Unit has detected an open circuit (open load) in the heater circuit of the Lambda (Oxygen/O2) sensor. This can be caused by a disconnected plug, a severed wire in the harness, or a burnt-out heater element inside the sensor itself.

• Farmall
• Puma
• MX/TG
• SR175
• SV212
• F5H
• NEF
• ISM/Cursor

1. 1

   Inspect the wiring harness and connectors between the Lambda sensor and the Engine ECU for disconnected plugs, chafed wires, or corroded pins.

2. 2

   Disconnect the Lambda sensor and use a multimeter to measure the resistance across the heater circuit pins on the sensor itself. An infinite resistance reading confirms the internal heater element is burnt out.

3. 3

   Turn the ignition key to the ON position and check for battery voltage at the heater power supply pin on the machine-side harness to rule out a blown fuse or broken supply wire.

4. 4

   Connect the Case IH Electronic Service Tool (EST) to read active/stored codes and monitor the Lambda sensor data.

1. 1

   Power Down

   Turn off the engine, remove the key, and allow the exhaust system to cool completely.

2. 2

   Disconnect

   Locate the Lambda sensor in the exhaust pipe and disconnect its electrical connector.

3. 3

   Remove Sensor

   If the sensor failed the continuity test, use a specialized O2 sensor socket to carefully unthread the Lambda sensor from the exhaust pipe.

4. 4

   Install New Sensor

   Apply a small amount of anti-seize compound to the threads of the new sensor (if not pre-applied) and thread it into the exhaust. Torque to the manufacturer's specification.

5. 5

   Reconnect

   Plug the sensor's electrical connector back into the engine wiring harness, ensuring the locking tab clicks into place.

6. 6

   ECU Reset

   Connect the Case IH Electronic Service Tool (EST). Navigate to the emissions configuration items, select the Lambda Sensor, and click 'CONFIGURE SELECTED ITEM' followed by 'RESET' to clear the ECU adaptations. Clear the 3713 fault code and run the engine to verify the code does not return.