Case IH F-4382-04 - ECU – Engine Control Unit (ECU): Aftertreatment 1 Outlet NH3 Gas Sensor Heater - Voltage below normal, or shorted to low source

Internal short circuit or open load error on the heater circuit/trim resistor line, which causes the sensor to underheat. The sensor cannot reach its required operating temperature to accurately measure ammonia slip in the exhaust stream.

• MAGNUM AFS Connect
• Farmall 110A
• Farmall 120A
• Farmall 130A
• Farmall 140A
• Farmall 110U
• Magnum
• Steiger
• Puma
• Maxxum
• Axial-Flow 20 Series
• Axial-Flow 240 Series
• Farmlift 935
• TV380 Compact Track Loaders
• 580N Backhoes

1. 1

   Inspect the wiring harness leading to the NH3 sensor (located at the outlet of the SCR catalyst) for chafing, melting, or rodent damage.

2. 2

   Disconnect the NH3 sensor and inspect the pins for corrosion, moisture, or pushed-out terminals.

3. 3

   Check for a short to ground or an open circuit on the sensor's heater power supply and ground lines.

4. 4

   Verify that the CAN bus communication lines to the NH3 sensor module are intact, as the sensor processor reports heater errors to the ECU via the CAN data bus.

5. 5

   Remove the sensor and inspect the tip for severe soot packing or crystallized Diesel Exhaust Fluid (DEF), which can insulate the sensor and cause heating anomalies.

1. 1

   Turn off the battery master disconnect switch.

   Ensure the machine is parked on a level surface with the engine off. The exhaust system must be completely cool before beginning this repair to prevent severe burns.

2. 2

   Locate the NH3 sensor.

   It is mounted in the exhaust stream at the downstream outlet of the SCR muffler/catalyst.

3. 3

   Remove the SCR muffler and catalyst upper heat shield.

   Perform this step if necessary for access.

4. 4

   Disconnect the electrical connector linking the NH3 sensor to the engine wiring harness.

5. 5

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

   Tip: If the sensor is seized, apply penetrating oil to the threads and allow it to sit before attempting removal.

6. 6

   Apply a high-temperature anti-seize compound to the threads of the new sensor.

   Do this if not already pre-applied by the manufacturer. Do not get anti-seize on the sensor tip.

7. 7

   Install the new NH3 sensor into the exhaust pipe and tighten to the OEM specified torque.

8. 8

   Reconnect the electrical connector.

   Ensure it clicks securely into place.

9. 9

   Reinstall any heat shields or exhaust clamps that were removed during disassembly.

10. 10

    Turn on the battery disconnect, start the engine, and use the Case IH Electronic Service Tool (EST) to clear the fault code.

    Perform any required SCR system resets or sensor calibrations.