Case IH 19198 (F-172-14) - ECU – Engine Control Unit (ECU): Plausibility check error of the second fresh air temperature sensor at cold start.

Upon a cold engine start, the control module monitors up to five different temperature sensors to ensure their readings are mutually plausible. If the second fresh air temperature sensor (often a combined temperature/humidity sensor) reports a value that deviates significantly from the other sensors, the system flags it as an implausible reading and logs this fault code.

• VESTRUM CVX
• Case IH Austoft 9900 Sugarcane Harvesters
• Case N-Series TLBs (Tractor Loader Backhoes)

1. 1

   Ensure the ignition switch is in the OFF position

2. 2

   Locate the fresh air temperature/humidity sensor (designated as sensor B-185)

3. 3

   Disconnect the sensor and use a multimeter to check the resistance across the sensor's receptacle pins (specifically Pin 1 and Pin 3 on connector X-185). The resistance should be approximately 2.5 kΩ at 20.0 °C (68.0 °F)

4. 4

   Visually inspect the wiring harnesses and connectors for damaged, bent, or pushed-back pins, corroded terminals, or chafed/broken wires

5. 5

   Flex the wiring harness while monitoring a diagnostic tool to check for intermittent shorts or breaks

1. 1

   Evaluate Sensor Resistance

   If the multimeter test shows the resistance is out of the 2.5 kΩ (at 68°F) specification, the sensor has failed internally. Proceed to replace the fresh air temperature sensor.

2. 2

   Evaluate Wiring

   If the sensor tests good but wiring damage is found during the visual inspection, repair the damaged wires or replace the affected harness section.

3. 3

   Software Check

   If both the sensor resistance and the wiring harness are within specification, the issue may be a software glitch. Verify that the ECU (A-028) has the latest software version installed. Re-flash or update the ECU software using the Case IH Electronic Service Tool (EST).

4. 4

   Clear and Verify

   After replacing the sensor or updating the software, clear the fault code from the ECU and perform a cold start to verify the code does not return.