New Holland ENG 3558 – Engine ECU: Info: Humidity Sensor possibly saturated with water droplets - Signal Ratio below Limit

The signal ratio from the intake air humidity sensor has dropped below the acceptable minimum threshold. The system logic infers that this abnormal reading is likely caused by the sensor's internal element becoming physically saturated with water droplets or heavy condensation, which distorts its ability to measure the intake air moisture accurately.

• T4
• T6000
• T7 series
• T7.185
• T7.225
• T7.250
• T8 series
• T9 series
• CR series
• CR6090
• CR9090
• CX series
• CX8080
• CX8090
• W-Series Wheel Loaders
• W110C
• W170C

1. 1

   Inspect the engine air intake system for obvious signs of water ingress. Check for a missing or damaged rain cap, cracked air filter housings, or compromised intake piping.

2. 2

   Remove the humidity sensor from the intake tract and physically inspect the probe for standing water droplets, heavy condensation, or debris.

3. 3

   Inspect the sensor's electrical connector and the wiring harness leading back to the Engine ECU. Look for trapped moisture inside the connector, corrosion on the pins, or chafed wires that could cause a short to ground.

1. 1

   Power down the machine and turn off the master battery disconnect switch.

   This prevents electrical spikes during the repair.

2. 2

   Locate the humidity sensor.

   It is mounted in the engine intake air filtration piping, typically between the air filter housing and the turbocharger/intake manifold.

3. 3

   Disconnect the electrical harness from the sensor.

4. 4

   Unbolt or unthread the humidity sensor from the intake pipe.

5. 5

   If the intake tract is wet, thoroughly dry the piping and resolve the root cause of the water ingress before proceeding.

6. 6

   Install the new replacement humidity sensor into the intake tract and secure it.

7. 7

   Reconnect the electrical harness.

   Ensure the weather seal clicks firmly into place.

8. 8

   Turn on the battery disconnect and connect a diagnostic tool.

   Use a tool such as the CNH Electronic Service Tool or Jaltest AGV.

9. 9

   Clear the inactive ENG 3558 fault code.

10. 10

    Perform a start-up counter reset or aftertreatment reset.

    Important Reset Step: If the engine was placed into a power derate or electronic limitation due to this emissions/intake fault, you must use the diagnostic tool to perform a 'start-up counter reset' or aftertreatment reset to restore full tractor operation.