New Holland DCU 19559 – DCU (Dosing Control Unit): Low UREA level 1 (warning) - UREA level below Limit 1 - P203F Reagent - fluid level in tank - too low

The Diesel Exhaust Fluid (DEF / Urea) level in the tank has dropped below the first warning threshold (Limit 1). This triggers the standard OBD2 emissions code P203F, indicating that the reductant fluid level is critically low.

• T5 Series
• T6 Series
• T7 Series
• T7.220
• T7.235
• T7.250
• T7.260
• T7.270
• T8 Series
• T8.390
• T8.410
• T9 Series
• CR series combines
• CR7.90
• CX series combines
• CX8.90
• FR forage harvesters

1. 1

   Physically check the DEF tank level and compare it to the in-cab gauge or sensor reading to verify if the tank is actually empty.

2. 2

   Inspect the DEF fluid quality and test for proper urea concentration (must be 32.5%). Poor-quality or crystallized fluid can mimic a sensor failure.

3. 3

   Examine the DEF level sensor (head unit) wiring harness and connectors for signs of corrosion, pin damage, or open circuits.

4. 4

   Check for accompanying codes such as P205B (temperature sensor fault) or P207F (DEF quality performance), which strongly point to a complete failure of the DEF head unit assembly.

1. 1

   Refill the Tank

   Fill the DEF tank with fresh, certified 32.5% Diesel Exhaust Fluid.

2. 2

   Clear Codes

   Cycle the key and use a diagnostic scan tool (like the CNH Electronic Service Tool) to clear the DCU 19559 / P203F fault codes.

3. 3

   Test Operation

   Run the machine to see if the code returns. If the code clears and the gauge reads accurately, the issue was simply a low fluid level.

4. 4

   Sensor Replacement (If necessary)

   If the tank is full but the code persists and the gauge remains empty, the DEF tank level sensor (integrated into the DEF Head Unit) has failed.

5. 5

   Install New Head Unit

   Disconnect the battery, drain the DEF tank (if required for access), disconnect the coolant lines and electrical harness from the DEF head unit, and remove the unit from the top of the tank. Install the replacement unit, reconnect the lines, and clear the codes.