Case IH 19456 – Engine Control Unit (ECU): Ambient temperature plausibility failure

This code triggers when the control module detects that the reading from the ambient temperature sensor does not make logical sense (is not "plausible") when compared to expected parameters or other temperature sensors on the machine (such as the intake air temperature or engine coolant temperature).

• Tier 4b
• Case N-Series Tractor Loader Backhoes (TLBs)
• Case 580N
• Case 580 Super N
• Case 590 Super N

1. 1

   Connect a diagnostic scan tool to the machine after it has been sitting overnight (cold engine) and compare the Ambient Temperature Sensor reading to the Intake Air Temperature (IAT) and Engine Coolant Temperature (ECT) sensors. They should all read within a few degrees of each other.

2. 2

   Inspect the wiring harness leading to the ambient temperature sensor for chafed wires, corrosion inside the connector, or bent pins, which can cause resistance and skew the temperature reading.

3. 3

   Disconnect the ambient temperature sensor while monitoring the scan tool. The reading should drop to a default extreme (typically -40°F/C). If the ECU responds, it verifies the wiring harness and ECU are functioning correctly, isolating the issue to the sensor.

1. 1

   Power Down

   Turn off the machine, remove the key, and engage the parking brake.

2. 2

   Locate the Sensor

   Locate the ambient temperature sensor. On Case Tier 4 equipment, this is often a combined "Humidity and Ambient Temperature Sensor" located near the engine air intake routing or cooling package.

3. 3

   Disconnect

   Press the release tab on the electrical harness connector and gently pull it away from the sensor.

4. 4

   Remove

   Unbolt or unclip the faulty ambient temperature sensor from its mounting bracket or intake tube.

5. 5

   Install

   Install the new replacement sensor into the mounting location.

6. 6

   Reconnect

   Plug the electrical harness back into the sensor, ensuring it clicks securely into place.

7. 7

   Clear Codes

   Connect your diagnostic scan tool, clear the 19456 fault code from the ECU/VCM, and cycle the ignition.

8. 8

   Verify

   Check the live data on the scan tool to ensure the ambient temperature is now reading the correct outside temperature.