Case IH 19458 – Engine Control Unit (ECU), Vehicle Control Module (VCM), or Dosing Control Unit (DCU): Ambient temperature is too low

The ambient temperature reading sent to the control module is implausibly low or out of range. A failure here can cause the engine to limit performance or torque due to SCR protection strategies.

• Tier 4b
• Magnum
• Steiger
• Puma
• Maxxum
• Farmall
• Optum
• Vestrum
• N-Series Tractor Loader Backhoes (TLBs)
• skid steers
• T5
• T6
• T7
• T8

1. 1

   Check if the vehicle was recently moved from a freezing environment into a heated shop/room after a long standstill, which can cause a temporary implausibility fault

2. 2

   Inspect the humidity/ambient temperature sensor and its wiring harness for physical damage, moisture, or corroded connector pins

3. 3

   Verify the machine's battery voltage, as low battery voltage (especially during cold cranking) can disable power stage diagnostics and cause erroneous sensor readings

4. 4

   Use the DATAR or EST diagnostic tool to read the live ambient temperature and humidity values. If the temperature reads an impossible negative value or the humidity is outside the 60%–85% range, the sensor is likely defective

1. 1

   Turn off the engine and disconnect the battery

   Turn off the engine and disconnect the battery to prevent electrical shorts.

2. 2

   Locate the sensor

   Locate the humidity/ambient temperature sensor. It is mounted on the engine air suction/intake pipe, downstream of the air filter.

3. 3

   Disconnect the electrical harness

   Disconnect the electrical harness connector from the sensor.

4. 4

   Remove the defective sensor

   Remove the defective sensor from the intake pipe.

5. 5

   Install the new sensor

   Wipe the mounting port clean and install the new humidity/ambient temperature sensor.

6. 6

   Reconnect the electrical harness

   Reconnect the electrical harness.

7. 7

   Reconnect the battery

   Reconnect the battery and power the unit on.

8. 8

   Verify and clear the fault code

   Connect the diagnostic tool, verify the ambient temperature reading is now accurate, and clear the fault code 19458.