New Holland ENG 3723 – Engine Control Module (ECM / ECU): Lambda sensor: LSU sensor temperature Ri is below the minimum limit.

The Engine Control Unit has detected that the internal resistance (Ri) of the Lambda (LSU wideband oxygen) sensor indicates its operating temperature is below the minimum required threshold. This condition is almost always caused by a failure of the sensor's internal heater element, a wiring fault in the heater power stage, or a failure within the ECU's heater control circuit.

• T4
• T5
• T5.95
• T6
• T7
• T7.260
• T7040
• T8
• T9
• Workmaster 60
• Workmaster 70
• CR9090
• CX8080 Elevation
• CX8090 Elevation
• L series
• C series
• W50C
• W80C

1. 1

   Inspect the wiring harness and the 5-wire/6-wire connector going to the Lambda sensor for melted insulation, corrosion, or loose pins.

2. 2

   Using a high-impedance digital multimeter (DMM), check for battery voltage and ground at the sensor's heater circuit pins (IA, IP, UN, VG). Do not use a standard analog multimeter as it draws too much current and can permanently damage the sensor.

3. 3

   Measure the internal resistance of the sensor's heater element to verify if it has an open circuit, which would prevent it from heating up.

1. 1

   Power Down

   Turn off the machine, remove the key, and disconnect the battery to prevent electrical shorts.

2. 2

   Locate the Sensor

   Locate the Lambda (O2) sensor on the exhaust system, typically mounted upstream of or near the DPF/SCR emissions assembly.

3. 3

   Disconnect

   Unplug the sensor's electrical connector.

4. 4

   Removal

   Using a specialized O2 sensor socket (to accommodate the wires), carefully unscrew the sensor from the exhaust bung. If it is seized, penetrating oil and heat may be required.

5. 5

   Preparation

   Apply a small amount of high-temperature anti-seize compound to the threads of the new sensor (if it does not come pre-applied). Caution: Do not get any anti-seize on the sensor tip, as this will contaminate and ruin the new sensor.

6. 6

   Installation

   Thread the new sensor in by hand to prevent cross-threading, then tighten it to the manufacturer's specified torque.

7. 7

   Reconnect

   Plug the electrical connector back in, ensuring the harness is secured and routed safely away from extreme exhaust heat.

8. 8

   Relearn/Calibration

   Reconnect the battery. Use the CNH Electronic Service Tool (EST / EASY tool) to clear the fault codes. You must re-flash or reset the control module to allow the ECU to learn the new sensor's calibration adjustments.