New Holland 3682 – ECU: Exhaust temperature: Fault Check for enhanced SCR – Min of First exhaust gas temperature

The Engine Control Unit (ECU) has detected that the exhaust gas temperature reading from the first sensor (upstream of the Selective Catalytic Reduction / SCR catalyst or Diesel Oxidation Catalyst / DOC) has fallen below the minimum expected threshold during operation. The SCR system requires a minimum operating temperature (typically around 190°C) to properly inject Diesel Exhaust Fluid (DEF/AdBlue) and reduce NOx emissions. When this temperature is not met or the sensor fails to report it accurately, the system cannot efficiently process emissions, which may lead to forced high-idle conditions or engine derating.

• T6 Series (T6.120 to T6.180)
• T7 Series (T7.165 to T7.270)
• T8 Series (T8.320 to T8.435)
• CR Series (CR7.90 to CR9.90)
• CX Series (CX8.80
• CX8.90)
• FR Forage Cruiser Series (FR480
• FR550
• FR650)

1. 1

   Check DEF Quality and Level: Ensure the Diesel Exhaust Fluid (DEF) is at an adequate level and has not crystallized or become contaminated, as poor DEF can cause SCR efficiency warnings and temperature irregularities.

2. 2

   Live Data Monitoring: Connect a diagnostic tool (such as CNH E.A.S.Y.) and monitor the live data for 'Exhaust Gas Temperature 1' (upstream of SCR). Verify if the temperature reading is stuck, erratic, or reading an impossible value (e.g., below ambient temperature when the engine is hot).

3. 3

   Electrical/Wiring Inspection: Inspect the wiring harness and connector for the first Exhaust Gas Temperature (EGT) sensor. Look for broken wires, melted insulation, or corrosion at the pins.

4. 4

   Sensor Resistance Test: Disconnect the sensor and measure its resistance with a multimeter. A healthy EGT sensor typically reads between 220 Ω and 240 Ω at ambient temperatures (0°C to 50°C). Voltage at the connector should be checked to ensure it is not dropping below 0.25V.

5. 5

   Physical Inspection: Check the exhaust pipe and SCR components for heavy soot buildup or crystallized DEF blocking the exhaust flow, which can skew temperature readings.

1. 1

   Cool Down

   Park the machine on a level surface, turn off the engine, and allow the exhaust system to cool completely to prevent severe burns.

2. 2

   Locate the Sensor

   Locate the first Exhaust Gas Temperature (EGT) sensor. It is threaded directly into the exhaust pipe/manifold upstream of the SCR/DOC assembly.

3. 3

   Disconnect Wiring

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

4. 4

   Remove the Sensor

   Using a properly sized wrench or specialized sensor socket, loosen and remove the faulty EGT sensor from the exhaust pipe. If the sensor is seized due to heat cycling, apply a penetrating fluid and allow it to soak before applying torque.

5. 5

   Prepare the New Sensor

   Apply a small amount of high-temperature anti-seize compound to the threads of the new sensor (if it does not come pre-applied from the factory). Do not get anti-seize on the probe tip.

6. 6

   Install the New Sensor

   Thread the new sensor into the exhaust pipe by hand to prevent cross-threading, then tighten it to the OEM torque specification.

7. 7

   Reconnect and Clear

   Reconnect the electrical harness. Turn the key to the ON position, connect your diagnostic tool, and clear the 3682 fault code.

8. 8

   Test Run

   Start the engine and run it under load (or perform a forced stationary regeneration) to ensure the exhaust temperature rises appropriately and the code does not return.