New Holland 1802 – Engine ECU: DPF Out Temp Sensor Low Voltage

The Engine Control Unit (ECU) has detected an abnormally low voltage signal from the temperature sensor located at the outlet of the Diesel Particulate Filter (DPF). This condition typically indicates a short circuit to ground in the wiring harness or an internal failure of the sensor itself. The ECU relies on this sensor to monitor the DPF's operational status and control the regeneration process; an incorrect low reading can prevent the DPF from regenerating and lead to severe exhaust system complications.

• L220
• T4 Series
• T-Series
• CX Combines

1. 1

   Visually inspect the DPF outlet temperature sensor and its wiring harness for physical damage, burnt or chafed wires, and ensure the connector is securely fastened and free of corrosion.

2. 2

   Check for a short circuit to ground by disconnecting the sensor from the main harness and using a multimeter to test for continuity between the signal wire at the harness connector and chassis ground.

3. 3

   Perform a sensor resistance test with the sensor disconnected. Measure resistance across its two pins and compare to manufacturer specifications (infinite resistance indicates an open circuit, zero resistance indicates a dead short).

4. 4

   Perform a dynamic sensor test by carefully warming the sensor with a heat gun and observing if the resistance changes smoothly as temperature increases.

5. 5

   Verify live data using the New Holland Electronic Service Tool (EST). With a cold engine, the sensor should read close to ambient air temperature. Impossible values (e.g., -40°C or a fixed high temperature) indicate a faulty sensor or circuit.

1. 1

   Isolate and secure the machine

   Park the machine on a level surface, lower all attachments, engage the parking brake, and turn off the engine. Allow the exhaust system to cool completely before beginning work to avoid burns.

2. 2

   Locate the correct sensor

   Identify the DPF OUT temperature sensor, which is threaded into the exhaust pipe immediately after the DPF housing. Ensure you are working on the post-DPF sensor, as there are multiple sensors in the exhaust system.

3. 3

   Repair wiring harness

   If a short or open circuit was found during diagnostics, repair the damaged section of the wiring harness. Ensure all connections are clean, secure, and protected from heat and abrasion.

4. 4

   Replace the DPF outlet temperature sensor

   If the sensor failed the resistance or live data tests, disconnect the electrical connector and unscrew the old sensor (use penetrating oil if seized). Thread the new sensor in by hand to avoid cross-threading, tighten to the manufacturer's specified torque, and reconnect.

5. 5

   Clear codes and verify repair

   Use a diagnostic tool to clear the 1802 fault code from the ECU's memory. Start the engine, monitor live data to ensure the new sensor is reading correctly, and perform a DPF regeneration to confirm the system is fully functional.