Case IH F-4382-07 - ECU – Engine Control Unit (EDC / Engine ECU): NH3 sensor heater performance failure

The NH3 (Ammonia) sensor failed to reach its heated-up state within a given time limit, or there is an internal short circuit/open circuit on the heater's minimum/maximum lines, indicating erratic, intermittent, or incorrect heater data.

• MAGNUM AFS Connect
• Steiger / Quadtrac (e.g., 620)
• Magnum
• Puma
• Maxxum
• Farmall A/U series (110A, 120A, 130A, 140A, 110U)
• 240 Series Axial-Flow Combines
• WD2505 High Speed Windrowers
• Case 580N Backhoes
• 821F/921F Wheel Loaders

1. 1

   Inspect the NH3 sensor wiring harness between the sensor controller and the sensor itself for any physical defects, melting, or chafing.

2. 2

   Check for short circuits to ground, short circuits to battery voltage, or open circuits on the heater lines.

3. 3

   Ensure there are no accompanying CAN bus communication errors (such as SPN 92EE 'NH3 sensor off-line'), which would indicate a harness failure rather than a sensor failure.

4. 4

   If the visual inspection and wiring checks are OK, conclude that the fault lies within the sensor's internal heater and prepare to replace the sensor.

1. 1

   Locate the NH3 sensor.

   It is mounted downstream of the SCR muffler / Clean Up Catalyst (CUC) in the exhaust pipe.

2. 2

   Remove heat shields if necessary.

   If necessary for access, remove the SCR muffler and catalyst upper heat shield.

3. 3

   Disconnect electrical connector.

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

4. 4

   Remove the NH3 sensor.

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

5. 5

   Install the new NH3 sensor.

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

6. 6

   Reconnect the electrical harness.

   Reconnect the electrical harness.

7. 7

   Reinstall heat shields.

   Reinstall any heat shields that were removed.

8. 8

   Verify the repair.

   Turn on the machine, clear the inactive fault codes via the diagnostic menu, and run the engine to allow the exhaust to heat up. Verify that the sensor reaches operating temperature and the code does not return.