Case IH 3519 – Engine Control Module (ECM): Ambient Air Temperature Sensor failure (of Humidity Sensor) - CAN Signal failure

The engine control system has lost CAN bus communication with the intake Humidity Sensor (which also houses the Ambient Air Temperature sensor). The controller is either receiving a corrupted CAN message or no signal at all from this specific sensor.

• Case IH Magnum Series (235, 250, 280, 310, 340, 380)
• Case IH Steiger Series
• Case IH Trident 5550
• Case IH Wheel Loaders (821F, 921F, 1121G2)

1. 1

   Inspect the wiring harness and connector at the humidity sensor for broken wires inside the protective conduit right behind the sensor connector (most common cause)

2. 2

   Disconnect the sensor and check for pushed-out pins, corrosion, or moisture intrusion inside the connector

3. 3

   Test the CAN High and CAN Low wires between the humidity sensor connector and the Engine ECU for continuity, open circuits, or shorts to ground/power

4. 4

   Remove the sensor and check if the element is physically damaged, heavily coated in soot/debris, or saturated with water droplets

1. 1

   Power Down

   Turn off the ignition and set the machine's main battery disconnect switch to the OFF position.

2. 2

   Locate the Sensor

   Open the engine hood. Locate the engine air intake tube, positioned just after the main air filter/cleaner assembly. The humidity sensor is mounted directly on this tube, usually next to the air restriction sensor.

3. 3

   Disconnect Wiring

   Carefully unplug the electrical connector from the humidity sensor.

4. 4

   Repair Wiring (If Applicable)

   If you found broken wires inside the conduit during your diagnostic checks, cut back the damaged wire, splice in a new connector pigtail/pins, and seal it with heat-shrink tubing.

5. 5

   Remove the Sensor

   If the wiring is intact and the sensor is deemed faulty, remove the mounting hardware/clip securing the humidity sensor to the air intake tube and pull the sensor out.

6. 6

   Install the New Part

   Insert the new humidity sensor into the intake tube and secure it.

7. 7

   Reconnect

   Plug the wiring harness back into the sensor, ensuring the locking tab clicks into place.

8. 8

   Test

   Turn the battery disconnect switch back on, start the engine, and verify via the cab display or diagnostic tool that fault code 3519 has moved from 'Active' to 'Inactive/Stored'. Clear the stored codes.