Case IH 19557 – Engine Control Module (ECM) / Engine ECU: NOx feed back fault detection

This fault code indicates an issue within the Selective Catalytic Reduction (SCR) system's feedback loop. The engine control system monitors the nitrogen oxide (NOx) reduction efficiency using NOx sensors located upstream and downstream of the SCR catalyst. Code 19557 is triggered when the system detects that the NOx levels are not dropping as expected, or when the sensor readings are implausible compared to the modeled NOx output.

• Tier 4b
• Magnum (180 through 370)
• Steiger / Quadtrac (350 through 600)
• Puma
• Maxxum
• Farmlift (632, 635, 735, 742, 935)
• Case CE 521F, 621F, 821F, 921F, 1021F, 1121F
• Combines (5130, 6130, 7130, 7230, 8230, 9230)

1. 1

   Check for accompanying codes related to the DEF system (e.g., DEF quality, DEF pressure, SCR catalyst temp) or specific NOx sensor circuit codes (such as 3528 for Plausibility failure, 3529 for Open Load, or 3530 for Short Circuit)

2. 2

   Inspect the NOx sensor wiring harness and its 5-pin MCON connector for corrosion, melting, or short circuits

3. 3

   Verify that the Diesel Exhaust Fluid (DEF / AdBlue) is not contaminated and that the DEF dosing pump is functioning correctly

4. 4

   Use a diagnostic electronic service tool or a dedicated NOx Tester Box to read live data from the upstream and downstream NOx sensors, and to check the catalyst efficiency percentage

1. 1

   Power Down

   Turn off the machine and disconnect the battery to prevent electrical spikes and ensure the exhaust system has cooled down.

2. 2

   Disconnect Sensor

   Locate the faulty NOx sensor (often positioned behind the catalyst) and disconnect its 5-pin electrical plug.

3. 3

   Remove Sensor

   Carefully unscrew the NOx sensor probe from the exhaust pipe.

4. 4

   Install New Sensor

   Thread the new NOx sensor into the exhaust bung. (Note: Do not use excessive anti-seize or allow any chemicals to touch the sensor tip, as this will ruin the sensor).

5. 5

   Reconnect

   Plug the sensor's control module back into the machine's wiring harness.

6. 6

   Clear Codes and Reset

   Connect a diagnostic tool to clear the DTCs. If the FPT engine was placed into a derate/inducement mode (torque limitation) due to the fault being detected three times within 40 hours, you must use the service tool to reset the inducement counter. The engine will then allow a restart to confirm the system is functioning normally.