Case IH 3404 – Engine ECU (EDC): Charge Air cooler : Signal error for Charge air cooler downstream Temperature

The engine control system has detected an implausible signal, open circuit, or short circuit from the Charge Air Cooler (CAC) downstream temperature sensor. This occurs when the signal voltage falls outside the normal operating threshold (typically < 0.092 V or > 4.90 V).

• Magnum
• Steiger
• Puma
• Maxxum
• Optum

1. 1

   Stop the engine and allow the charge air cooler piping to cool completely before starting work

2. 2

   Visually inspect the CAC downstream temperature sensor on the intake piping, along with its harness and connectors, for physical damage

3. 3

   Disconnect the sensor and check for damaged, pushed-back, or loose connector pins, as well as debris or water ingress inside the housing

4. 4

   Check for damaged or loose machine earths (grounds) and test the circuit for a short to ground, short to battery, or an open circuit

5. 5

   Perform a resistance test on the sensor (thermistor resistance should change inversely with temperature); if resistance is completely open or shorted, the sensor has failed

1. 1

   Turn off the ignition, remove the key, and ensure the engine is cool.

2. 2

   Disconnect the negative battery terminal if repairing the wiring harness.

3. 3

   Unplug the electrical connector from the CAC downstream temperature sensor.

4. 4

   If wiring damage or corrosion was found during diagnostics, repair the harness or replace the connector pigtail.

5. 5

   If the wiring is sound, use a wrench to carefully unthread the faulty CAC temperature sensor from the intake/charge air piping.

6. 6

   Install the new OEM replacement sensor.

   Do not overtighten, as this can damage the sensor threads or the intake pipe.

7. 7

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

8. 8

   Reconnect the battery, turn on the ignition, and use a CNH EST diagnostic tool (or compatible code reader) to clear the inactive 3404 fault code.

9. 9

   Start the engine and verify that the code does not return and that the engine is no longer in a derated power mode.