Case IH 3853 – Engine ECU / EDC (Electronic Diesel Control): Lambda sensor : Oxygen concentration implausibly high in part load operation.

The engine is running in a lean condition (too much air or not enough fuel) during part-load operation, or the sensor is falsely reading an excess of oxygen in the exhaust stream. This can be caused by unmetered air entering the system, a lack of fuel delivery, an exhaust leak upstream of the sensor, or a failure of the Lambda (Oxygen) sensor itself.

• Tractors
• Combines
• FPT NEF engines
• FPT F5C engines
• FPT Tier 3 engines
• FPT Tier 4a engines
• FPT Tier 4b engines

1. 1

   Check for Exhaust Leaks: Inspect the exhaust manifold and piping upstream of the Lambda sensor. A crack or blown gasket can draw fresh air into the exhaust stream, causing a falsely high oxygen reading.

2. 2

   Check for Intake Leaks: Inspect the intake manifold and charge air cooler piping for unmetered air leaks.

3. 3

   Inspect Fuel Delivery: Verify fuel pressure and check for fuel inlet restrictions or air ingress into the fuel supply. Low fuel pressure or restricted injectors will cause a lean condition.

4. 4

   Wiring and Connector Inspection: Check the Lambda sensor's electrical connector and wiring harness for melting, corrosion, or loose pins.

5. 5

   Check for Accompanying Codes: Look for other active codes related to fuel pressure, EGR deviation, or MAF sensors, which might point to the root cause of the lean condition.

1. 1

   Preparation

   Ensure the engine and exhaust system have completely cooled down to prevent severe burns.

2. 2

   Disconnect Power

   Disconnect the negative battery terminal to prevent electrical shorts and to help reset the ECU.

3. 3

   Locate the Sensor

   Locate the Lambda (O2) sensor on the exhaust system. It is typically threaded into the exhaust pipe near the catalytic converter or DPF unit.

4. 4

   Disconnect Wiring

   Push the release tab on the sensor's electrical connector and pull the two halves apart to disconnect it from the engine harness.

5. 5

   Remove the Sensor

   Use a specialized oxygen sensor socket or a wrench to unscrew the sensor. Note: If the sensor is seized due to exhaust heat cycles, apply a penetrating lubricant to the threads and let it sit, or carefully apply heat to the surrounding metal to break the corrosion.

6. 6

   Prepare the New Sensor

   Check if the new sensor has anti-seize compound pre-applied to the threads. If not, apply a small amount of high-temp anti-seize to the threads (be very careful not to get any on the sensor tip).

7. 7

   Install the New Sensor

   Thread the new sensor into the exhaust pipe by hand to ensure it does not cross-thread, then tighten it to the manufacturer's torque specification.

8. 8

   Reconnect

   Plug the electrical connector back into the wiring harness until it clicks.

9. 9

   Clear Codes

   Reconnect the battery, start the engine, and use an OBD/diagnostic scan tool to clear the 3853 fault code. Test run the machine at part-load to verify the code does not return.