Case IH 3557 – Engine Control Unit (ENG / ECU): Info: Humidity Sensor possibly saturated with water droplets - Signal Ratio above Limit

This code indicates that the engine's humidity sensor is reading a signal ratio that exceeds the acceptable limit, likely because the sensor element has become physically saturated with water droplets or excessive moisture in the intake air stream.

• Case IH Magnum 235 – 340 (Series 4)
• Case IH Steiger series
• Case IH Puma series
• Case IH Maxxum series
• Case IH WD1505 Windrowers

1. 1

   Inspect the engine air intake piping, air filter housing, and rain cap for signs of water ingress, pooling water, or snow accumulation.

2. 2

   Remove the humidity sensor and inspect the sensing element. If it is visibly wet, dry it carefully with ambient air (do not use high-pressure compressed air directly on the element).

3. 3

   Inspect the sensor's electrical connector and wiring harness for moisture, corrosion, or chafing. Water inside the connector can short the signal and trigger this code.

4. 4

   Clear the fault code using a diagnostic tool and run the machine at operating temperature to see if the code returns. If the code persists or returns immediately, the sensor has likely failed internally.

1. 1

   Locate the Sensor

   Locate the humidity sensor on the engine air intake piping/manifold (usually positioned between the air filter housing and the turbocharger inlet).

2. 2

   Disconnect Power

   Turn off the machine's ignition and disconnect the battery ground if required by standard safety procedures.

3. 3

   Disconnect the Harness

   Carefully unplug the electrical connector from the humidity sensor.

4. 4

   Remove the Sensor

   Unbolt or unthread the humidity sensor from the intake pipe.

5. 5

   Clean the Port

   Wipe the mounting port on the intake pipe with a clean, lint-free rag to ensure no dirt or debris falls into the engine intake.

6. 6

   Install the New Sensor

   Insert the new humidity sensor (OEM Part # 87482355) into the port and secure it to the manufacturer's torque specifications.

7. 7

   Reconnect the Harness

   Plug the electrical connector back into the sensor, ensuring it clicks and locks into place.

8. 8

   Clear Codes

   Reconnect the battery, turn on the ignition, and use a diagnostic tool to clear the 3557 fault code. Start the engine and verify that the code does not return.