Case IH 19814 – Engine Control Unit (ECU): SRC low for Charge air cooler downstream Temperature

Signal Range Check Low. The Engine Control Unit has detected that the voltage signal from the Charge Air Cooler Downstream Temperature Sensor (Intake Manifold Temperature Sensor or Boost Temperature Sensor) has dropped below the minimum acceptable threshold (typically near 0 volts). This condition almost always indicates a short circuit to ground in the sensor's wiring circuit or an internal short/failure within the sensor itself.

• Tier 4b
• Magnum
• Maxxum
• Puma
• Steiger series
• N-Series Loader Backhoes
• Skid Steers
• Compact Track Loaders

1. 1

   Visually inspect the Charge Air Cooler Downstream Temperature Sensor connector and wiring harness for chafing, melted insulation, or corrosion that could cause a short to ground.

2. 2

   Perform a voltage check: Disconnect the sensor, turn the key to the ON position (engine off), and use a multimeter to check the reference voltage from the ECU at the harness connector (should be a steady 5V).

3. 3

   Perform a short to ground test: With the sensor and battery disconnected, test the signal wire for continuity to a known good ground. Continuity indicates the wiring harness is shorted to ground.

4. 4

   If the wiring harness tests good, perform a sensor resistance test. The sensor itself is likely shorted internally, pulling the signal voltage low.

1. 1

   Turn off the machine, remove the key, and disconnect the negative battery cable to prevent electrical spikes.

2. 2

   Locate the Charge Air Cooler Downstream Temperature Sensor on the intake manifold or the charge air cooler outlet pipe.

3. 3

   Disconnect the electrical harness plug from the sensor.

4. 4

   Using the appropriate wrench or deep socket, unthread the faulty sensor from the intake manifold.

5. 5

   Inspect the mounting port and clean any soot or debris from the threads.

6. 6

   Install the new sensor.

   Check if the new sensor requires thread sealant; many OEM sensors come with a pre-applied thread locker/sealant. Torque to OEM specifications.

7. 7

   Reconnect the electrical harness plug until it clicks securely into place.

8. 8

   Reconnect the battery, turn the key on, and use a diagnostic scan tool (like the CNH EST tool) to clear the inactive 19814 fault code.

9. 9

   Start the engine and verify that the code does not return and that the intake manifold temperature reads correctly on the live data stream.