Case IH 19050 – Engine Control Unit (ECU): Downstream NOx sensor supply voltage is out of range

The Engine Control Unit (ECU) has detected that the electrical voltage supplying the downstream NOx sensor module is outside the expected operating parameters (either too high or too low), pointing to an electrical, wiring, or internal sensor module failure.

• Tier 4b
• Magnum (180-380)
• Puma (150-220)
• Steiger / Quadtrac (350-620)
• Maxxum
• Farmall
• 240 Series (7240, 8240, 9240)
• 130/140 Series (5130-7140)
• Patriot (2250-4440)
• Titan (3030-4540)

1. 1

   Inspect the 5-pin MCON electrical connector at the downstream NOx sensor module for corroded pins, moisture intrusion, or chafed wires leading back to the ECU

2. 2

   Measure the supply voltage at the sensor harness to ensure the alternator or voltage converter is providing the correct voltage (typically 12V or 24V)

3. 3

   Inspect the exhaust piping between the SCR catalyst and the downstream NOx sensor for exhaust leaks that could skew readings

4. 4

   Ensure the machine is reaching proper operating temperatures to complete the dew point warm-up cycle

5. 5

   Remove the sensor and visually inspect the tip for heavy white crystallization (DEF) or thick black soot indicating an upstream issue

1. 1

   Preparation

   Turn off the machine, remove the key, and disconnect the negative battery cable. Allow the exhaust system to cool completely.

2. 2

   Locate the Sensor

   Locate the downstream NOx sensor, which is threaded into the exhaust tailpipe directly after the SCR / Clean Up Catalyst (CUC).

3. 3

   Disconnect Electronics

   Unplug the sensor's electrical connector from the machine's wiring harness. Unbolt the sensor's control module box from its mounting bracket.

4. 4

   Remove the Sensor

   Using a specialized NOx sensor socket (usually 22mm) or a wrench, carefully unscrew the sensor probe from the exhaust pipe.

5. 5

   Clean the Boss

   Clean the threads of the exhaust bung with a thread chaser to ensure the new sensor seats correctly.

6. 6

   Install the New Sensor

   Apply a small amount of high-temperature anti-seize to the threads of the new sensor (if it does not come pre-applied). Thread the sensor in by hand to prevent cross-threading, then tighten to the OEM torque specification (usually around 50 Nm / 37 lb-ft).

7. 7

   Route and Reconnect

   Mount the new sensor's control module box. Route the wiring harness exactly as it was from the factory, ensuring it is secured away from extreme heat sources or sharp edges. Reconnect the electrical plug.

8. 8

   Clear Codes

   Reconnect the battery. Connect the Case IH Electronic Service Tool (EST) to the diagnostic port and clear the inactive fault codes.

9. 9

   Validation

   Run the machine through a warm-up cycle under load to allow the ECU to recognize the new sensor and verify that the SCR system is functioning properly.