Case IH 3718 – Engine Control Unit (ECU) / Electronic Diesel Control (EDC): Lambda sensor : Oxygen concentration implausibly low in overrun

The Lambda (Oxygen) sensor is reading an oxygen concentration that is lower than expected during an overrun condition (when the machine is decelerating or coasting and fuel injection is cut off). This indicates that either the sensor is malfunctioning, there is an exhaust leak, or fuel is still entering the cylinders and combusting.

• Farmall series (85A, 95A, 105A, 115A, 115U, 100C)
• Puma series
• Maxxum series
• Steiger / Quadtrac series
• Axial-Flow Combines (5130, 6130, 7130, 5140, 6140)

1. 1

   Check the Lambda sensor wiring harness for shorts to the battery or ground, and verify battery voltage (low voltage can cause false readings).

2. 2

   Check for fuel system leakage, such as leaking electronically controlled injectors or a mechanically stuck open fuel cut-off valve (unintended fuel delivery consumes oxygen).

3. 3

   Inspect the exhaust system upstream of the Lambda sensor for leaks that could skew the sensor's readings.

4. 4

   Check the low-pressure fuel supply for inlet restrictions or air entering the fuel supply system.

1. 1

   Safety First

   Disconnect the battery, ensure the equipment is blocked, and avoid moving parts before performing maintenance.

2. 2

   Locate the Sensor

   Locate the Lambda sensor on the exhaust system, typically near the EGR exhaust treatment unit or pressure differential unit.

3. 3

   Clear Access

   If necessary, loosen the system heat shield and remove the bonnet support to gain clear access to the left-hand side of the engine.

4. 4

   Disconnect

   Unplug the electrical harness connector from the Lambda sensor.

5. 5

   Remove

   Carefully unscrew the Lambda sensor from the exhaust pipe.

6. 6

   Install

   Thread the new Lambda sensor into the exhaust pipe and tighten to the OEM specified torque.

7. 7

   Reassemble

   Reconnect the electrical harness, reinstall the heat shield, and reattach the bonnet support.

8. 8

   Clear Codes

   Reconnect the battery and use a diagnostic tool to clear the EDC fault codes.