Case IH 17538 (F-3216-14) - ECU – Engine Control Module (ECM) / Denox Module: NOx Sensor Up Stream - Sensor value implausible as compared to the software model

The upstream Nitrogen Oxide (NOx) sensor (located before the SCR catalytic converter) is reporting a measurement deviation. The physical reading from the sensor does not match the expected value calculated by the control module's internal software model.

• VESTRUM CVX
• Case IH Farmall series
• Case IH MX / TG series
• Case IH Magnum series
• Other CNH Industrial / AGCO Power platforms

1. 1

   Cold Start Occurrence: Note that this specific implausibility code can sometimes be triggered erroneously during a cold start.

2. 2

   Voltage Supply: Check for a battery defect or alternator defect. Both high battery voltage and low voltage can cause sensor errors.

3. 3

   Wiring and Connections: Inspect the wiring harness for the upstream NOx sensor. Look for wiring defects, short circuits, or connection problems causing too high resistance.

4. 4

   ECU Verification: Rule out an internal ECU defect, which is listed as a potential underlying cause for this signal deviation.

1. 1

   Test the Charging System

   Verify that the battery and alternator are functioning correctly and providing stable voltage to the ECM and Denox module.

2. 2

   Inspect the Harness

   Trace the wiring from the upstream NOx sensor to the ECM/Denox module. Check for chafing, melted wires near the exhaust, or corrosion in the connectors.

3. 3

   Test Resistance

   Use a multimeter to ensure there is no high resistance in the sensor's communication lines.

4. 4

   Replace the Sensor

   If the battery, alternator, and wiring are all in good condition, the upstream NOx sensor itself has failed or degraded and must be replaced.

5. 5

   Clear Codes

   Clear the fault codes from the ECM/Denox module and run the machine to ensure the software model and sensor readings align.