Case IH 19811 – Engine Control Module (ECM): Physical Range Check low for Charged Air cooler downstream temperature

This code indicates an electrical circuit fault where the signal from the Charge Air Cooler (CAC) downstream temperature sensor has fallen below the minimum acceptable physical range, typically pointing to a short to ground, an open circuit, or a failed sensor.

• Tier 4b
• Case IH agricultural equipment
• Case Construction equipment
• N-Series Tractor Loader Backhoes
• Tier 4 Final FPT engines
• NEF 4.5L
• NEF 6.7L

1. 1

   Visual Inspection: Locate the Charge Air Cooler downstream temperature sensor (typically mounted on the cold-side charge air pipe between the intercooler and the intake manifold, or directly on the intake manifold). Inspect the wiring harness and connector for chafing, melted insulation, corrosion, or pushed-out pins.

2. 2

   Voltage Check: Disconnect the sensor. With the Key On, Engine Off (KOEO), use a multimeter to check the reference voltage at the harness connector. You should typically see a 5V reference signal from the ECM. If voltage is missing, the issue is in the wiring harness or the ECM.

3. 3

   Resistance/Continuity Check: Measure the resistance across the sensor's terminals. If the sensor reads as an open circuit (infinite resistance) or a dead short (0 ohms), the sensor has failed internally.

4. 4

   Harness Short Check: Check for continuity between the signal wire and a known good ground. If there is continuity, the wiring harness is shorted to ground, which directly causes a Range Check Low condition.

1. 1

   Disconnect battery

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

2. 2

   Locate sensor

   Locate the Charge Air Cooler downstream temperature sensor on the intake piping/manifold.

3. 3

   Unplug connector

   Depress the locking tab and carefully unplug the electrical connector.

4. 4

   Remove faulty sensor

   Using an appropriately sized deep socket or wrench, unthread the faulty sensor from the charge air pipe.

5. 5

   Inspect and clean port

   Inspect the mounting port for heavy soot or oil buildup and clean it if necessary.

6. 6

   Install new sensor

   Thread the new sensor into the port by hand to prevent cross-threading, then tighten to the OEM torque specification (do not over-tighten, as these sensors are often brass or plastic and can snap).

7. 7

   Reconnect harness

   Reconnect the electrical harness, ensuring the locking tab clicks into place.

8. 8

   Reconnect battery

   Reconnect the battery.

9. 9

   Clear fault code and verify

   Connect a diagnostic scan tool (such as the CNH Electronic Service Tool) to clear the inactive 19811 fault code and verify that the sensor is now reading a plausible ambient/intake temperature.