Case IH 19446 – Engine Control Unit (ECU) / Engine Control Module (ECM): Fault Check for enhanced SRC-Max of Fourth exhaust gas temperature

This code indicates a diagnostic plausibility failure regarding the 4th Exhaust Gas Temperature (EGT) sensor in the Selective Catalytic Reduction (SCR) system. The system runs a model-based plausibility check (SRC-Max) to ensure the exhaust temperatures are reaching the required thresholds for proper emissions reduction. When the 4th EGT sensor reports a temperature that is out of the expected range or fails to rise appropriately, this code is triggered.

• Tier 4b
• Farmall 100C
• Farmall 105A/C/U
• Farmall 110A/C/U
• Farmall 115A/C/U
• Farmall 120U
• Maxxum 120
• Maxxum 125
• Maxxum 130
• Maxxum 140
• Puma 140
• Steiger/Magnum 5130
• Steiger/Magnum 5140
• Steiger/Magnum 7130
• Steiger/Magnum 7140
• Steiger/Magnum 7230
• Steiger/Magnum 7240
• SR210
• SR220
• SR250
• SV250
• SV300
• TR270
• TR320
• TV380
• 1021F/G
• 1121F/G

1. 1

   Visually inspect the 4th EGT sensor (furthest downstream) wiring harness and connector for chafing, melting, corrosion, or loose pins.

2. 2

   Perform a cold soak test using the CNH Electronic Service Tool (EST) after the machine has sat overnight. EGT sensors 1, 2, 3, and 4 should all read within a few degrees of ambient temperature. If sensor 4 is skewed, it is likely faulty.

3. 3

   Inspect the exhaust piping immediately upstream of the 4th sensor for exhaust leaks, which can introduce cool air or allow hot gases to escape, preventing accurate temperature readings.

4. 4

   Check for accompanying codes related to DEF dosing, SCR efficiency, or EGT circuit voltages (e.g., short to ground/battery), which would point to a hard electrical failure rather than a plausibility fault.

1. 1

   Power Down

   Turn off the machine and disconnect the battery via the master disconnect switch to prevent electrical shorts.

2. 2

   Locate the Sensor

   Identify the 4th exhaust gas temperature sensor on the SCR/exhaust aftertreatment assembly.

3. 3

   Disconnect Wiring

   Carefully unplug the sensor's electrical connector from the main engine harness.

4. 4

   Remove the Sensor

   Apply penetrating fluid to the threads of the sensor bung if the exhaust is rusted. Use an EGT sensor socket or a line wrench to carefully back the sensor out of the exhaust pipe.

5. 5

   Install the New Sensor

   Apply a small amount of high-temperature anti-seize to the threads of the new sensor (if not pre-applied from the factory). Thread it in by hand to prevent cross-threading, then tighten to the OEM torque specification.

6. 6

   Reconnect

   Plug the sensor back into the wiring harness and secure the cable with zip ties to ensure it does not rest against hot exhaust components.

7. 7

   Clear and Test

   Reconnect battery power. Connect the CNH EST diagnostic tool, clear the 19446 fault code, and perform a stationary forced DPF/SCR regeneration to verify that the 4th EGT sensor temperature rises smoothly and passes the system's plausibility checks.