Case IH 3173 – Engine Control Unit (ECU) / Engine Controller: ISM-IDI Aftertreatment Burner Temperature Sensor Low Voltage

The voltage signal returning from the temperature sensor on the Diesel Particulate Filter (DPF) burner assembly has dropped below the minimum acceptable threshold. This typically points to a short circuit to ground in the sensor wiring, a failed sensor element, or a disconnected/corroded connector.

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1. 1

   Inspect the wiring harness leading to the Aftertreatment Burner Temperature Sensor for melting, chafing, or heat degradation causing a short to ground.

2. 2

   Disconnect the sensor and inspect the pins for pushed-out pins, moisture intrusion, corrosion, or a loose connection.

3. 3

   Turn the key to the ON position (engine off) and check for the proper 5V reference signal at the harness connector.

4. 4

   Measure the resistance across the sensor's pins. A reading of 0 ohms (dead short) or infinite resistance (open circuit) indicates internal sensor failure.

5. 5

   Check continuity between the sensor connector and the Engine ECU pins to ensure there is no break in the wiring harness.

1. 1

   Cool Down

   Ensure the machine is turned off and the exhaust/DPF system has completely cooled down to prevent severe burns.

2. 2

   Disconnect Power

   Disconnect the negative battery cable to protect the ECU.

3. 3

   Locate the Sensor

   Locate the Aftertreatment Burner Temperature Sensor, which is threaded directly into the DPF burner/combustion chamber assembly.

4. 4

   Disconnect

   Unplug the electrical connector from the sensor.

5. 5

   Remove the Sensor

   Using an appropriately sized wrench or sensor socket, carefully unscrew the sensor. Note: Apply penetrating oil to the threads and allow it to soak if the sensor is stuck to avoid stripping the housing threads.

6. 6

   Prepare the New Sensor

   If the new sensor does not have pre-applied anti-seize, apply a small amount of high-temperature, sensor-safe anti-seize compound to the threads (avoid getting any on the sensor probe itself).

7. 7

   Install

   Thread the new sensor into the burner housing by hand to prevent cross-threading, then tighten to the OEM torque specification.

8. 8

   Reconnect

   Plug the electrical connector back in, ensuring the locking tab clicks securely. Route the wiring away from direct heat sources.

9. 9

   Clear Codes

   Reconnect the battery. Connect the CNH Electronic Service Tool (EST) to clear the inactive 3173 fault code.

10. 10

    Verify

    Run the engine and monitor the burner temperature via the EST. Perform a stationary DPF regeneration to ensure the burner ignites and the sensor reads the temperature climb accurately without throwing a code.