Case IH 3408 – Engine Control Unit (ECU) / EDC (Electronic Diesel Control): Lambda Sensor: Oxygen Concentration Implausibly High

The Engine Control Module calculates the expected oxygen concentration in the exhaust based on the actual air flow and the actual fuel injection quantities. This fault code is triggered when the measured oxygen value from the lambda (O2) sensor falls outside of the normal operating range, indicating an implausibly high oxygen level (a lean condition).

• skid steer
• Tractors (Farmall, Magnum, Puma, Optum series)
• Skid Steer Loaders (SR175, SV series)
• Combines and Harvesters

1. 1

   Inspect the exhaust manifold and piping upstream of the lambda sensor for cracks, blown gaskets, or loose clamps (exhaust leak cause).

2. 2

   Check for blocked fuel lines, clogged fuel filters, or failing injectors (genuine lean condition cause).

3. 3

   Inspect the wiring harness leading to the lambda sensor for melted wires, corrosion in connector pins, or chafing.

4. 4

   Use the CNH EST or EASy diagnostic tool to monitor live voltage and oxygen concentration readings from the lambda sensor.

1. 1

   Preparation

   Turn off the machine, remove the key, and disconnect the battery to prevent electrical shorts. Ensure the exhaust system has completely cooled down.

2. 2

   Disconnect

   Locate the lambda sensor on the exhaust pipe/DPF assembly. Carefully unplug the sensor's electrical connector from the engine wiring harness.

3. 3

   Removal

   Using an O2 sensor socket or a wrench, loosen and remove the lambda sensor from the exhaust pipe. (Penetrating oil may be required if the sensor is seized).

4. 4

   Installation

   Apply a small amount of high-temperature anti-seize compound to the threads of the new lambda sensor (if it does not come pre-applied). Thread the sensor into the exhaust pipe by hand to prevent cross-threading, then tighten to the OEM torque specification.

5. 5

   Reconnect

   Plug the new sensor's electrical connector back into the engine harness. Reconnect the battery.

6. 6

   ECU Reset

   Connect the CNH diagnostic tool (EST/EASy) to the machine. Clear the 3408 fault code and perform the "Reset ECU data (Lambda sensor)" configuration so the engine control module can calibrate to the new sensor.

7. 7

   Verification

   Start the engine and let it reach operating temperature to verify the code does not return.