Case IH 19573 – Engine Control Module (ECM/ECU) or Aftertreatment Control Module (ACM): SRC Min error for the NOx signal

The Engine Control Unit (ECU) has detected that the signal from the Nitrogen Oxide (NOx) sensor is reading below the minimum expected threshold. The system flags the sensor data as unreliable, which will typically trigger an SCR failure warning, an emissions light, and eventually force the tractor into a power-reduction 'derate' or limp mode.

• Tier 4b
• Magnum series (180, 190, 210, 225, 235, 260, 290, 315, 340, 370, 380)
• Puma series (130 to 230)
• Maxxum series (110 to 150)
• Farmall series
• Steiger and Quadtrac series (350, 370, 400, 420, 450, 470, 500, 550, 600)
• Axial-Flow series (5130, 6130, 7130, 7230, 8230, 9230)
• Farmlift series (632, 635, 735, 742, 935)
• 521F
• 621F
• 821F
• 921F
• 1021F
• 1121F
• Titan series (2240, 3030, 3530, 4030, 4530)

1. 1

   Check DEF (AdBlue) quality — ensure the fluid is fresh and the tank is free of sediment, as contaminated DEF causes SCR failure and triggers plausibility codes.

2. 2

   Check for other active codes — address any DEF dosing system codes first (e.g., pump pressure, injector blockages) because a lack of DEF will cause the NOx sensor to read incorrectly.

3. 3

   Inspect the wiring harness — check the 5-pin connector and the wiring leading to the ECM for signs of abrasion, melting, or water intrusion.

1. 1

   Locate the Sensor

   Identify whether the code is for the upstream NOx sensor (before the DOC/SCR) or the downstream NOx sensor (after the SCR catalyst in the exhaust tailpipe).

2. 2

   Disconnect Battery/Power

   Ensure the machine is turned off and the exhaust system has completely cooled down.

3. 3

   Disconnect the Electrical Plug

   Unplug the 5-pin MCON electrical connector linking the NOx sensor to the machine's harness.

4. 4

   Remove the Sensor

   Use a sensor socket or wrench to unscrew the NOx sensor from the exhaust pipe bung (typically an M20x1.5 thread).

5. 5

   Install the New Sensor

   Thread the new NOx sensor into the exhaust pipe and tighten to OEM torque specifications.

6. 6

   Route the Wiring

   Carefully route the new sensor's wiring harness. Ensure no connectors are mounted vertically where water can pool. Provide a 'drip loop' in the wiring approaching the connector from below to prevent water intrusion, and use mounting clips to keep the wire away from sharp edges or extreme heat sources.

7. 7

   Clear Codes

   Reconnect the electrical plug. Use a CNH diagnostic tool to clear the 19573 fault code. A single error clearing is usually required after fitting the new sensor to reset the SCR system and remove the power derate.