Case IH 19179 (DTC 1CBE) - ECU – Engine Control Unit (ECU): Downstream NOx sensor self-diagnosis result is higher than the limit.

The downstream NOx sensor is located directly after the Selective Catalytic Reduction (SCR) catalyst in the exhaust system. It measures the nitrogen oxide pollutants making it through the Diesel Oxidation Catalyst (DOC) and SCR before they exit the tailpipe. This fault code is triggered when the sensor performs its internal self-diagnostic check and the resulting value exceeds the maximum allowable threshold. This typically indicates a failure of the sensor itself, though it can also be influenced by wiring issues or severe catalyst inefficiency.

• MAXXUM T4E
• 240 Series Axial-Flow Combines (7240, 8240, 9240)
• Steiger
• Magnum
• Puma (150, 165, 185, 200, 220)
• Optum (270, 300 CVT)
• Farmall (110A, 120A, 130A, 140A)
• T7 Series
• Wheel Loaders (1021G Tier 4B)

1. 1

   Check Sensor Readiness (Dew Point): Ensure the engine has completed a full warm-up cycle to see if the sensor returns to a 'Ready' status, as moisture must be wicked off the tip.

2. 2

   Inspect Wiring and Connectors: Inspect the 5-cavity female wire connector and the harness leading to the downstream NOx sensor for chafing, melting, or corrosion.

3. 3

   Check for Accompanying Codes: Look for other active SCR/DEF codes (such as DEF quality or dosing system faults) that might cause abnormally high NOx readings and skew sensor self-diagnostics.

1. 1

   Turn the key switch to the OFF position

   Allow the exhaust system to cool completely.

2. 2

   Locate the downstream NOx sensor

   The sensor is threaded into the exhaust pipe directly after the SCR catalyst.

3. 3

   Disconnect the electrical harness

   Disconnect the 5-pin electrical harness connector from the sensor.

4. 4

   Remove the faulty NOx sensor

   Use a sensor socket or wrench to carefully unthread and remove the faulty NOx sensor from the exhaust pipe.

5. 5

   Apply anti-seize compound

   Apply a small amount of anti-seize compound to the threads of the new sensor (if not already pre-applied by the manufacturer). Do not get any compound on the sensor tip.

6. 6

   Install the new downstream NOx sensor

   Torque it to the manufacturer's specification.

7. 7

   Reconnect the electrical harness

   Reconnect the 5-pin electrical harness connector.

8. 8

   Clear fault codes and run warm-up cycle

   Turn the key switch ON, clear the fault codes using a diagnostic tool, and run the engine through a warm-up cycle to allow the new sensor to reach its 'Ready' state.