New Holland DCU 19264 – DCU: Tank heating Valve | Open load | P20B1 Reagent - tank heating valve - open circuit

The system has detected an open circuit in the DEF (Diesel Exhaust Fluid / AdBlue / Reagent) tank heater coolant valve solenoid circuit. This means the electrical connection to the valve is broken, unplugged, or the solenoid coil inside the valve has failed internally.

• T6 Series
• T6.140
• T7 Series
• T7.170
• T7.270
• T8 Series
• T8.275
• T8.320
• T8.360
• Crawler Dozers (D180C)
• Wheel Loaders (W190B)

1. 1

   Inspect the wiring harness leading to the DEF tank heater control valve for bare spots, chafing, or broken wires.

2. 2

   Ensure the electrical connector at the valve is securely plugged in and free of corrosion.

3. 3

   Use a multimeter to measure the resistance across the pins of the DEF heater control valve solenoid (infinite resistance indicates a blown internal coil).

4. 4

   Verify that the DEF coolant hoses are routed correctly, as backward installation can cause continuous hot coolant circulation and valve damage.

1. 1

   Clear the Code

   Save the error log in your Electronic Service Tool (EST) and then erase the code.

2. 2

   Repair Wiring

   If a broken wire or damaged connector was found during the diagnostic phase, repair the harness and restart the ECU to see if the fault clears.

3. 3

   Replace the Valve

   If the wiring is intact but the solenoid is internally open or sticking, the heater control valve must be replaced. Drain the coolant or pinch off the coolant lines, disconnect the electrical connector, remove the hose clamps and detach the coolant lines. Unbolt the old valve and install the new one, ensuring the directional flow is correct. Reconnect the hoses, clamps, and electrical connector.

4. 4

   Final Verification

   Top off any lost engine coolant. Restart the ECU/tractor and verify that the DCU 19264 / P20B1 code does not return and the system exits its derate protocol.