Case IH 19017 – Engine Control Unit (ECU / EDC) and NH3 sensor controller: NH3 sensor signal out of range failure

The NH3 (Ammonia) sensor is sending a voltage or data signal that falls outside of the expected operational parameters, indicating either a failed sensor, a wiring harness issue, or an extreme imbalance in the exhaust gas composition.

• Tier 4b
• 240 Series Axial-Flow (7240, 8240, 9240)
• 6150
• 8250
• Steiger/Quadtrac (e.g., 620)
• Puma (e.g., 220 CVT)
• Maxxum 115
• Farmall 110A
• Farmall 120A
• Farmall 130A
• Farmall 140A
• Farmall 110U
• Case 580N Backhoe Loaders

1. 1

   Inspect the NH3 sensor and its wiring harness for physical damage, melting, or chafing.

2. 2

   Disconnect the 8-pin connector at the NH3 sensor controller and check for pushed pins, corrosion, or moisture intrusion (do not force multimeter pins directly into the ECU connector).

3. 3

   Verify that the C-CAN bus is online. If multiple SCR sensors are offline, unplug components one by one (such as the DEF quality sensor or NOx sensors) to see if the CAN bus communication returns, which would indicate a shorted module.

4. 4

   Ensure the DEF/AdBlue fluid is uncontaminated. Poor DEF quality can cause abnormal exhaust readings that may trigger sensor range faults.

1. 1

   Turn off the engine, remove the key, and disconnect the battery.

   Allow the machine to cool completely before servicing, as the exhaust system operates at extreme temperatures.

2. 2

   Locate the NH3 sensor on the exhaust pipe.

   It is located downstream of the Clean Up Catalyst (CUC) and SCR muffler.

3. 3

   Remove the SCR muffler and catalyst upper heat shield.

   Perform this step only if necessary for access.

4. 4

   Disconnect the 8-pin electrical connector from the NH3 sensor controller.

5. 5

   Carefully unscrew and remove the Ammonia (NH3) sensor from the exhaust pipe.

6. 6

   Thread the new NH3 sensor into the exhaust pipe.

   Tighten to the OEM torque specification.

7. 7

   Route the sensor wire away from extreme heat sources and reconnect the 8-pin connector.

   The sensor wire is typically 700mm long.

8. 8

   Reinstall any heat shields that were removed.

9. 9

   Reconnect the battery, turn on the machine, and clear the fault code.

   Use a diagnostic service tool to clear the 19017 / 38EE fault code. Run the engine to operating temperature to verify the code does not return.