Case IH 19437 – Engine Control Module (ECM): NOx Difference between upstream and calculated value

This fault code indicates a plausibility error regarding the engine's exhaust emissions. The Upstream NOx sensor (located in the exhaust stream before the Diesel Oxidation Catalyst / DOC) is measuring a Nitrogen Oxide (NOx) level that differs significantly from the expected NOx value calculated by the engine control module based on current operating parameters (such as RPM, load, and fuel rate).

• Tier 4b
• Steiger (335, 420, 580)
• Quadtrac (370, 420, 450, 470, 500, 540, 550)
• Magnum (340 Rowtrac)
• Maxxum (110, 115, 130, 145)
• Puma
• Optum
• Patriot (2250, 3240, 3340)
• Wheel Loaders (521G through 1121G)

1. 1

   Check for other active fault codes related to the intake manifold temperature, fuel pressure, EGR system, or DEF dosing system, as an actual engine issue could cause the physical NOx output to legitimately differ from the calculated model.

2. 2

   Inspect the 5-pin electrical connector and wiring harness leading to the Upstream NOx sensor for chafing, corrosion, or loose terminal pins.

3. 3

   Verify CAN bus communication to ensure the network is communicating properly with the NOx sensor.

4. 4

   Inspect for exhaust leaks prior to the DOC and Upstream NOx sensor, as well as intake air leaks, which can skew the actual NOx output.

1. 1

   Turn off machine and disconnect battery

   Turn off the machine and disconnect the battery via the battery disconnect switch (BDS) to prevent electrical shorts.

2. 2

   Locate Upstream NOx sensor

   Locate the Upstream NOx sensor in the exhaust pipe, positioned before the Diesel Oxidation Catalyst (DOC).

3. 3

   Disconnect electrical connector

   Disconnect the 5-cavity electrical wire connector from the sensor.

4. 4

   Remove faulty sensor

   Carefully unscrew and remove the faulty Upstream NOx sensor from the exhaust pipe.

5. 5

   Install new sensor

   Install the new Upstream NOx sensor into the exhaust pipe and tighten to the manufacturer's specified torque.

6. 6

   Reconnect electrical connector

   Reconnect the 5-pin electrical connector.

7. 7

   Turn on battery disconnect switch

   Turn the battery disconnect switch back on.

8. 8

   Clear fault code

   Connect a diagnostic tool (such as CNH EST or Jaltest) to clear the 19437 fault code.

9. 9

   Test engine

   Run the engine and perform a test cycle to ensure the code does not return and that the engine exits any torque derate conditions.