Case IH 19768 – Engine Control Module (ECM) or Vehicle Control Module (VCM): SCR catalyst upstream temperature sensor plausibility max threshold

This fault code indicates that the temperature reading from the Selective Catalytic Reduction (SCR) upstream temperature sensor is implausibly high. The control module compares the sensor's reading against expected operating models or other exhaust temperature sensors (like the DOC or downstream SCR sensors). If the reading exceeds the maximum plausible threshold for the current engine load and state, this code is triggered.

• Tier 4b
• Steiger
• Magnum
• Maxxum
• Farmall
• Quadtrac
• AFX 6130
• AFX 8250
• N-Series Loader Backhoes
• Farmlift telehandlers

1. 1

   Perform a cold soak comparison using the Electronic Service Tool (EST) to ensure the SCR upstream temperature sensor reads identically to ambient air, DOC, and SCR downstream sensors.

2. 2

   Inspect the sensor wiring harness for chafing, melting, or shorts to power, and check connector pins for oxidation or corrosion.

3. 3

   Perform a disconnect test: unplug the sensor and monitor the EST. If the reading remains implausibly high instead of showing an open circuit, the wiring harness is shorted to power or the ECU is faulty.

4. 4

   Conduct an operational test by running the machine until the SCR upstream temperature reaches 300 - 330 °C (572 - 626 °F) and monitor for erratic jumps or dropouts.

1. 1

   Preparation

   Turn off the engine, disconnect the battery, and allow the exhaust system to cool completely to avoid severe burns.

2. 2

   Locate the Sensor

   Locate the SCR upstream temperature sensor. It is threaded into the exhaust pipe between the Diesel Oxidation Catalyst (DOC) / Mixer and the SCR catalyst, just upstream of the DEF/AdBlue dosing module.

3. 3

   Disconnect Electrical

   Unplug the 2-cavity electrical connector connecting the sensor to the engine harness.

4. 4

   Remove the Sensor

   Carefully unscrew the temperature sensor from the exhaust bung. Note: Exhaust sensors frequently seize. Apply penetrating oil and allow it to soak if resistance is high to prevent stripping the exhaust pipe threads.

5. 5

   Install New Sensor

   Thread the new SCR upstream temperature sensor into the exhaust bung and tighten to the manufacturer's specified torque.

6. 6

   Reconnect

   Plug the electrical connector back in and reconnect the battery.

7. 7

   Clear Codes

   Connect the Electronic Service Tool (EST) and clear fault code 19768.

8. 8

   Validation

   Start the engine and perform a test run under load to ensure the exhaust temperature reads plausibly and the code does not return.