Case IH 19547 – Engine Control Module (ECM) or Dosing Control Unit (DCU) / Vehicle Control Module (VCM): SRC Max error for the NOx signal

Signal Range Check (SRC) Maximum error for the Nitrogen Oxide (NOx) sensor. The engine control system has detected that the signal coming from the NOx sensor is reading above the maximum expected or physically possible limit (out of range high). This is typically a plausibility error indicating that the sensor itself has failed, there is a short-to-voltage in the sensor wiring, or the sensor is heavily contaminated.

• Tier 4b
• Magnum 180
• Magnum 190
• Magnum 200
• Magnum 210
• Magnum 220
• Magnum 225
• Magnum 235
• Magnum 240
• Magnum 250
• Magnum 260
• Magnum 280
• Magnum 290
• Magnum 310
• Magnum 315
• Magnum 340
• Magnum 370
• Puma 150
• Puma 165
• Steiger 350
• Steiger 400
• Steiger 450
• Steiger 500
• Steiger 550
• Steiger 600
• Quadtrac 350
• Quadtrac 400
• Quadtrac 450
• Quadtrac 500
• Quadtrac 550
• Quadtrac 600
• Axial-Flow 5130
• Axial-Flow 5140
• Axial-Flow 6130
• Axial-Flow 6140
• Axial-Flow 7130
• Axial-Flow 7140
• Axial-Flow 7230
• Axial-Flow 7240
• Axial-Flow 8230
• Axial-Flow 8240
• Axial-Flow 9230
• Axial-Flow 9240
• Patriot 2250
• Patriot 3240
• Patriot 3340
• Patriot 4440
• Titan 3030
• Titan 3040
• Titan 3530
• Titan 3540
• Titan 4030
• Titan 4040
• Titan 4530
• Titan 4540

1. 1

   Check for accompanying codes (such as 19549, 19551, or 19536). If present, the issue is almost certainly electrical rather than a chemical emissions failure.

2. 2

   Inspect the 5-pin connector at the NOx sensor module for melted wires, chafing against the hot exhaust, water intrusion, or bent pins.

3. 3

   Verify that the NOx sensor is receiving proper power (12V or 24V depending on machine architecture) and has a solid ground.

4. 4

   Check for exhaust leaks upstream of the NOx sensor, which can introduce excess oxygen and skew sensor readings.

5. 5

   Check DEF quality and the dosing valve. Severely degraded DEF or a failing dosing valve can sometimes cause extreme NOx readings that trigger plausibility faults.

1. 1

   Power Down

   Turn off the machine, remove the key, and disconnect the battery to prevent electrical spikes. Allow the exhaust system to cool completely.

2. 2

   Locate the Sensor

   Locate the faulty NOx sensor on the exhaust/SCR aftertreatment pipe.

3. 3

   Disconnect

   Unplug the sensor's electrical connector from the main wiring harness. Unclip the sensor wire from any heat shields or retaining brackets.

4. 4

   Remove the Sensor

   Using a specialized NOx sensor socket or a 22mm wrench, carefully unscrew the sensor from the exhaust bung (M20x1.5 thread). Apply penetrating oil to the threads and let it sit if the sensor is seized to avoid stripping the exhaust bung.

5. 5

   Install the New Sensor

   Thread the new NOx sensor into the exhaust bung by hand to prevent cross-threading. Tighten to the OEM specified torque (usually around 50 Nm / 37 lb-ft).

6. 6

   Route Wiring

   Route the new sensor's wiring harness exactly as the old one was routed, ensuring it is secured away from direct contact with the hot exhaust pipe. Reconnect the 5-pin electrical plug.

7. 7

   Clear Codes

   Reconnect the battery. Connect a diagnostic scan tool (such as the CNH Electronic Service Tool) to clear the 19547 fault code.

8. 8

   Validation

   Start the engine and allow it to reach operating temperature. You may need to perform a forced stationary regeneration or an SCR system test via the diagnostic tool to initialize the new sensor and verify the repair.