Case IH 19517 – Engine Control Unit (ECU): Intake air humidity is too low

This fault indicates that the signal from the Intake Air Humidity Sensor is reading implausibly low or has dropped below the minimum allowable threshold. A 'too low' reading typically points to a short circuit to ground in the sensor wiring or an internally failed sensor.

• Tier 4b
• Case IH tractors and combines equipped with NEF 4 and NEF 6 engines (e.g., F4DFE series)
• Case N-Series Tractor Loader Backhoes (e.g., 580N, 590SN)

1. 1

   Visually inspect the sensor housing on the intake piping for physical damage or water droplets/moisture on the sensor element, which can skew the reading or short the element.

2. 2

   Disconnect the sensor and inspect the pins for corrosion, pushed-back pins, or moisture intrusion.

3. 3

   Check the wiring harness for a short circuit to ground. Verify that the sensor is receiving its 5V reference supply and has a good ground path back to the ECU.

4. 4

   Use the Case IH Electronic Service Tool (EST) to monitor the live physical signal of the Induction Air Humidity Sensor. If the value is pinned at an implausibly low baseline despite good wiring, the sensor is defective.

1. 1

   Turn the machine off, remove the key, and turn off the master battery disconnect switch.

   Ensure the machine is fully powered down before beginning repairs.

2. 2

   Locate the Intake Air Humidity Sensor on the main air intake tube, downstream of the air filter housing but upstream of the turbocharger inlet.

   Identify the sensor location for removal.

3. 3

   Depress the locking tab and disconnect the electrical harness from the sensor.

   Carefully remove the connector.

4. 4

   If circuit testing revealed a short to ground in the harness, trace the wire back to the ECU and repair the chafed/shorted section.

   Address any wiring faults before replacing the sensor.

5. 5

   If the wiring is intact, remove the mounting screws or unthread the defective Intake Air Humidity Sensor from the intake pipe.

   Remove the faulty sensor from the intake plumbing.

6. 6

   Install the replacement sensor. Ensure the O-ring or sealing gasket is properly seated to prevent unmetered air or dust from entering the engine.

   Proper sealing is critical to prevent engine damage from dust or unmetered air.

7. 7

   Reconnect the electrical harness until the locking tab clicks.

   Ensure a secure electrical connection.

8. 8

   Restore battery power, turn the key on, and use a diagnostic tool to clear the 19517 fault code. Start the engine and verify that the live humidity reading is now plausible and the code does not return.

   Verify the repair was successful and the system is reading correctly.