Case IH 19812 – Engine Control Unit (ECU): Signal error for Charge air cooler downstream Temperature

This fault code indicates that the engine control module is receiving an implausible signal, or detecting an open/short circuit, from the temperature sensor located downstream of the charge air cooler (intercooler).

• Tier 4b
• Case N-Series loaders
• Magnum tractors

1. 1

   Inspect the wiring harness and the connector at the charge air cooler downstream temperature sensor for chafing, corrosion, moisture, or backed-out pins.

2. 2

   Disconnect the sensor and the ECU harness, then check for continuity on the signal and ground wires between the sensor connector and the ECU pins.

3. 3

   Test the sensor wiring for a short to ground (which would trigger a related 'SRC Low' code like 19814) or a short to battery voltage (which triggers 'SRC High').

4. 4

   Measure the resistance across the sensor's terminals. If the sensor reads completely open (infinite resistance) or shorted (zero resistance) at ambient temperature, the sensor itself has failed internally.

1. 1

   Power Down

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

2. 2

   Locate the Sensor

   Locate the charge air cooler downstream temperature sensor. It is mounted on the charge air piping (intake tract) between the outlet of the charge air cooler and the engine's intake manifold.

3. 3

   Disconnect

   Press the release tab and carefully unplug the electrical connector from the sensor.

4. 4

   Remove Sensor

   Using an appropriately sized deep socket or wrench, unscrew the faulty temperature sensor from the intake pipe.

5. 5

   Install New Sensor

   Thread the new sensor into the port by hand to prevent cross-threading. Tighten it to the OEM torque specification (do not overtighten, as the sensor body is often brass or plastic and can break).

6. 6

   Reconnect

   Plug the electrical connector back into the sensor until it clicks securely.

7. 7

   Clear Codes

   Reconnect the battery, turn the ignition on, and use a CNH EST (Electronic Service Tool) or compatible OBD scanner to clear the inactive fault codes.

8. 8

   Test Run

   Start the engine and allow it to reach operating temperature to verify that the fault code 19812 does not return.