New Holland DCU 19092 – DCU: Monitoring VDD11 voltage - Dosing valve supply voltage high P0659 12 Volt supply for dosing module - above upper limit

The 12-volt supply circuit (VDD11) providing power to the DEF (Diesel Exhaust Fluid) dosing module is reading a voltage that exceeds the acceptable maximum threshold. This condition typically points to a short circuit to battery (SC2VBAT) in the wiring harness, an overcharging alternator, or an internal electrical short within the dosing module or the control unit itself.

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1. 1

   System Voltage Check: Verify the machine's overall battery voltage and alternator output to ensure the charging system is not overcharging and causing a system-wide high voltage spike.

2. 2

   Visual Inspection: Disconnect the DEF dosing module and inspect the electrical connector. Look for corrosion, bent pins, or DEF fluid ingress, as crystallized urea can cause severe electrical shorts.

3. 3

   Harness Testing: Using a multimeter, test the VDD11 supply circuit wiring between the DCU and the dosing module. Check for a short to battery voltage along the harness routing. Look for chafed wires or melted insulation near the hot exhaust components.

4. 4

   Component Isolation: If the wiring harness tests good, the fault is likely an internal short within the DEF dosing valve itself or, less commonly, a failure within the DCU.

1. 1

   Turn off the machine, remove the key, and disconnect the battery

   Prevents electrical spikes during the repair.

2. 2

   Locate the DEF dosing module

   The module is mounted on the exhaust SCR catalyst/mixing pipe.

3. 3

   Disconnect the electrical harness

   Carefully disconnect the electrical harness from the dosing module.

4. 4

   Disconnect the DEF fluid lines and coolant lines

   If equipped with a heated doser, disconnect the coolant lines. Be prepared to catch any spilled DEF or coolant, and cap the lines immediately to prevent system contamination.

5. 5

   Repair or replace the wiring harness

   If the diagnostic checks revealed a shorted wiring harness, repair the damaged wires or replace the affected harness section.

6. 6

   Remove the dosing module

   If the dosing module is internally shorted, remove the mounting hardware and extract the dosing valve from the exhaust pipe.

7. 7

   Clean the mounting boss

   Clean the mounting boss on the exhaust pipe thoroughly. Remove any crystallized DEF deposits from the tip area and mounting surface.

8. 8

   Install the new dosing module

   Torque the mounting hardware to OEM specifications, and reconnect the fluid/coolant lines and electrical connector.

9. 9

   Reconnect the battery

10. 10

    Clear fault codes

    Use a diagnostic scan tool to clear the DCU 19092 / P0659 fault codes.

11. 11

    Verify the repair

    Start the engine and operate the machine under load to increase the exhaust temperature (typically needs to exceed 150°C) to verify that the SCR system engages, dosing resumes, and the code does not return.