Case IH 3517 – Engine Control Unit (ECU) / A-9000: Ambient Air Temperature Sensor failure (of Humidity Sensor) - Signal too high

The engine controller has detected that the voltage in the B-9105 temperature signal circuit is higher than expected (greater than 4.95 V for longer than 500 ms). This typically points to an open circuit or a short-to-power in the sensor or its wiring harness.

• Farmall
• skid steer
• Steiger T4B
• Case IH 240 Series Axial-Flow Combines
• Case IH Magnum 235 - 340 (Series 4) Tractors
• Case IH STX Steiger Tractors (350 to 600 HP)

1. 1

   Locate the combined Humidity and Ambient Air Temperature sensor at the engine air intake.

2. 2

   Inspect the B-9105 sensor connector and the associated wiring harness leading back to the A-9000 ECU for physical damage, corrosion, or pushed-out pins.

3. 3

   Use a multimeter to test the signal wire for a short to a high-voltage source (power) or a complete break (open circuit).

1. 1

   Power down the machine and turn the battery disconnect switch to the OFF position.

2. 2

   Locate the Ambient Air Temperature / Humidity sensor at the engine intake.

3. 3

   Carefully disconnect the electrical connector from the sensor.

4. 4

   If the diagnostic circuit tests revealed a wiring issue (short to power or open wire), repair the harness segment between the B-9105 connector and the A-9000 ECU.

5. 5

   If the wiring is intact and the sensor itself has failed internally, remove the mounting hardware securing the sensor to the intake.

6. 6

   Remove the faulty sensor and install the replacement, securing it with the mounting hardware.

7. 7

   Reconnect the electrical connector.

8. 8

   Restore battery power, turn the key to the ON position, and use a diagnostic service tool to clear the 3517 / 19C4 fault code. Start the engine to verify the code does not return.