New Holland ENG 3722 – Engine Control Unit (ECU) / EDC7: Lambda Sensor: LSU sensor temperature Ri exceeds the maximum limit.

The engine utilizes a Bosch LSU-style wideband Lambda (Oxygen / O2) sensor to measure the oxygen content in the exhaust gas. This sensor relies on an internal heater to reach operating temperature, and the engine computer monitors this temperature by measuring the sensor's internal resistance (Ri). Fault code ENG 3722 is triggered when the internal temperature measurement (Ri) exceeds the maximum allowable limit programmed into the software. This typically indicates that the sensor is overheating due to a failed internal heater control, a degraded sensor element, or abnormally high exhaust gas temperatures.

• T4
• T5
• T6
• T7
• T8
• T9
• CR9090
• CX8080 Elevation
• CX8090 Elevation
• W50C ZB
• W60C ZB
• W70C HS
• W70C
• W80C HS
• W80C

1. 1

   Inspect the 5-wire Lambda sensor harness and connector for melting, corrosion, or physical damage.

2. 2

   Scan the ECU for accompanying circuit codes (e.g., 3724, 3725, 3711, 3712). If present, the issue is likely a wiring short or ECU fault rather than the sensor itself.

3. 3

   Verify exhaust temperatures are not genuinely excessive due to over-fueling or a malfunctioning DPF regeneration cycle.

1. 1

   Turn off the engine, disconnect the battery, and allow the exhaust system to cool completely to avoid burns.

2. 2

   Locate the Lambda sensor on the exhaust pipe.

   It is typically positioned upstream, before the catalytic converter or DPF/SCR assembly.

3. 3

   Disconnect the electrical connector from the Lambda sensor.

4. 4

   Using a specialized oxygen sensor socket or wrench, carefully unscrew the faulty Lambda sensor from the exhaust pipe.

   (Penetrating oil may be required if the threads are seized).

5. 5

   Apply a small amount of high-temperature anti-seize compound to the threads of the new sensor (if it does not come pre-applied from the manufacturer).

   Caution: Do not get anti-seize on the sensor tip, as this will contaminate it.

6. 6

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

7. 7

   Reconnect the electrical connector, ensuring the wiring is routed safely away from hot exhaust components.

8. 8

   Reconnect the battery, use a diagnostic scan tool to clear the ENG 3722 fault code, and run the engine to verify the code does not return.