New Holland 19325 – DCU or SCR controller: Urea Temperature in Tank Out of Allowable Range

The Dosing Control Unit (DCU) has detected that the voltage signal from the urea (DEF) tank temperature sensor is either higher or lower than the expected range for the current operating conditions. This illogical reading indicates that the reported temperature is inaccurate. Accurate DEF temperature readings are critical for the proper operation of the Selective Catalytic Reduction (SCR) system, as the system relies on this data to activate the DEF heater when temperatures approach freezing (12°F / -11°C). Associated SAE Code: P205B - Reductant Tank Temperature Sensor Circuit Range/Performance.

• T6 Series
• T7 Series
• Magnum Series
• Maxxum Series
• Puma Series
• FR Series
• CR Series
• CX Series
• Sprayers
• Windrowers
• Grape Harvesters
• Farmall 110A
• Farmall 120A
• Farmall 130A
• Farmall 140A

1. 1

   Check DEF quality and level: Ensure the tank is filled with fresh fluid meeting ISO 22241 standards. Use a refractometer to verify urea concentration is between 31.8% and 33.3%.

2. 2

   Visually inspect the wiring harness and electrical connector at the DEF tank sensor for damage, loose pins, or corrosion (look for white crystal deposits or green corrosion).

3. 3

   Perform a 'Cold Soak' rationality check: After sitting overnight, compare the DEF tank temperature reading with ambient air and engine coolant temperatures via a diagnostic tool. They should be nearly identical; significant deviation indicates a drifted or failed sensor.

4. 4

   Perform a wiring 'wiggle' test: With the machine on and a diagnostic tool displaying live DEF temperature data, wiggle the sensor harness to check for sharp spikes or dropouts indicating an intermittent connection.

5. 5

   Test sensor resistance: Disconnect the sensor and measure resistance across the temperature pins with a multimeter. Compare to manufacturer specs (e.g., 0°C/32°F = 942 ohms, 10°C/50°F = 608 ohms, 25°C/77°F = 330 ohms, 40°C/104°F = 189 ohms, 50°C/122°F = 133 ohms). Infinite or zero resistance confirms a faulty sensor.

1. 1

   Observe safety precautions

   Wear appropriate personal protective equipment (PPE), including gloves and eye protection, as DEF can be a skin and eye irritant.

2. 2

   Drain the DEF tank

   If the tank is not empty, drain the DEF into a clean, suitable container.

3. 3

   Access the sensor

   Depending on the machine model, remove the DEF tank from its mounting brackets if necessary to gain access to the top where the sensor/header unit is located.

4. 4

   Remove the old sensor unit

   Disconnect the electrical connector. Remove the retaining clips, screws, or locking ring securing the sensor assembly to the tank, and carefully lift the old unit out.

5. 5

   Clean and install the new sensor

   Clean the mounting surface on the tank, using hot water to dissolve any DEF crystallization. Install the new sensor assembly, ensuring the seal is properly seated, and secure it with the original hardware.

6. 6

   Reconnect and refill

   Reconnect the electrical connector, reinstall the DEF tank if it was removed, and refill the tank with fresh, uncontaminated DEF.

7. 7

   Clear codes and verify repair

   Use a diagnostic tool to clear fault code 19325 and any related SCR codes. Start the machine, allow the system to run, and monitor live data to ensure the new sensor reports a plausible temperature.