New Holland 3684 – EDC: Exhaust temperature – Fault Check for enhanced SRC – Max of Second exhaust gas temperature.

This code indicates that the system has detected an abnormally high reading from Exhaust Gas Temperature (EGT) Sensor 2. This is typically triggered when the sensor's signal voltage exceeds the maximum threshold (e.g., above 6.55 V), which points to either a short circuit to a high voltage source, a failed sensor, or a genuine over-temperature condition within the Selective Catalytic Reduction (SCR) or Diesel Particulate Filter (DPF) exhaust system.

• T6 and T7 Series Tractors (e.g.
• T6010-T6070)
• CX Series Combines (e.g.
• CX860
• CX880)
• B-Series Loader Backhoes (e.g.
• B90B
• B115B)

1. 1

   Connect the CNH Electronic Service Tool (E.A.S.Y.) to the diagnostic connector to confirm code 3684 is currently active.

2. 2

   Check the live temperature and voltage readings for EGT Sensor 2. If the sensor reads an impossibly high temperature or a voltage above 6.55 V while the exhaust is cold, the issue is electrical (sensor or wiring) rather than mechanical.

3. 3

   Inspect the wiring harness leading to EGT Sensor 2. Look for chafed wires, melted insulation, or a short circuit to a high-voltage source. Check the connector pins for corrosion or water ingress.

4. 4

   Ensure the sensor is properly mounted and threaded into the exhaust pipe. A loose or improperly distanced sensor can cause erratic readings.

5. 5

   If the sensor reading is plausible under load, inspect the SCR/DPF system for blockages or dosing valve malfunctions that could be causing a genuine exhaust over-temperature event.

1. 1

   Cool down exhaust

   Turn off the engine and allow the exhaust aftertreatment system to cool completely to prevent severe burns.

2. 2

   Locate EGT Sensor 2

   Locate Exhaust Gas Temperature Sensor 2. It is typically mounted in the exhaust piping just in front of the Diesel Oxidation Catalyst (DOC) or the DPF/SCR unit (often the middle sensor in a multi-sensor setup).

3. 3

   Disconnect harness

   Carefully unplug the electrical connector linking the EGT sensor to the engine wiring harness.

4. 4

   Remove the sensor

   Using a suitable wrench or specialized EGT sensor socket, carefully unscrew the sensor from the exhaust housing. If seized, apply penetrating oil and allow it to soak before applying force to avoid stripping the exhaust bung threads.

5. 5

   Install new sensor

   Thread the new EGT sensor into the exhaust port by hand to prevent cross-threading. Tighten it to the manufacturer's specified torque.

6. 6

   Reconnect wiring

   Plug the electrical connector back into the engine harness, ensuring it clicks securely into place.

7. 7

   Clear codes

   Reconnect the Electronic Service Tool, clear fault code 3684 from the EDC memory, and start the engine.

8. 8

   Validate repair

   Monitor the live exhaust gas temperature data while the engine warms up to ensure the new sensor is reading correctly and the fault code does not return.