Case IH 19457 – Engine Control Module (ECM) or Vehicle Control Module (VCM): Ambient temperature is too high

The sensor measuring the outside ambient air temperature is reporting a value to the system that exceeds the maximum allowable threshold.

• Tier 4b
• Case N-Series TLBs
• Case IH Tier 4B tractors
• Case IH Tier 4B combines

1. 1

   Check the ambient temperature sensor's mounting location to ensure it is not being subjected to an abnormal heat source (e.g., missing exhaust heat shields, blocked ventilation, or direct sunlight exposure).

2. 2

   Use a diagnostic scan tool to read the live ambient temperature data from the ECM and compare this reading to the actual outside temperature; if the reading is maxed out, the sensor is likely shorted.

3. 3

   Inspect the wiring harness leading to the ambient temperature sensor for chafing, melted insulation, or pinched wires.

4. 4

   Check the connector for corrosion, moisture, or backed-out pins.

1. 1

   Disconnect Power

   Turn off the machine and disconnect the battery ground to prevent electrical spikes.

2. 2

   Locate the Sensor

   Locate the ambient air temperature sensor (typically mounted near the front grille, intake manifold, or outside the cab, away from direct engine heat).

3. 3

   Remove the Sensor

   Unplug the electrical connector from the sensor. Unthread or unclip the sensor from its mounting bracket.

4. 4

   Install the New Sensor

   Install the replacement sensor and secure it. Reconnect the electrical harness, ensuring the weather-pack seal clicks into place.

5. 5

   Clear Codes

   Reconnect the battery, turn the key to the ON position, and use a CNH diagnostic tool (EST) to clear the 19457 fault code from the ECM/VCM.

6. 6

   Verify Repair

   Start the machine and monitor the live ambient temperature data to ensure it reads accurately and the code does not return.