New Holland DCU 19037 – DCU (Dosing Control Unit): Sensor supply 2 (5V internal; for UREA pressure sensors) — Supply Voltage too high

This code indicates that the 5-volt reference circuit (Sensor Supply 2) inside the control unit, which powers the Diesel Exhaust Fluid (DEF/Urea) pressure sensor, is detecting a voltage that is too high. This typically means the circuit is shorted to a higher voltage source (like battery power), or there is an internal short within the sensor or the control module itself.

• T5 Series
• T6 Series
• T6.155
• T6.165
• T7 Series
• T7.220
• T7.270
• T8 Series
• T9 Series
• W190B
• 721F-921F
• LM Series
• LM5040
• LM5060

1. 1

   Inspect the wiring harness between the DCU and the DEF pump supply module for chafing, melted insulation, or pinched wires that could cause the 5V sensor wire to short against a 12V/24V battery power wire.

2. 2

   Disconnect the DEF pressure sensor/pump module and the DCU. Check the pins for corrosion, bent terminals, or DEF fluid ingress (crystallization), which is highly conductive and can bridge circuits.

3. 3

   With the sensor disconnected and the key ON, use a multimeter to measure the voltage at the 5V reference pin on the harness connector. If it reads battery voltage (12V+), the harness is shorted to power. If it reads exactly 5V, the short is likely internal to the sensor itself.

4. 4

   If the harness tests perfectly fine (no continuity to power) but the 5V pin at the DCU outputs battery voltage, check for an internal hardware failure in the DCU.

1. 1

   Disconnect Power

   Turn off the machine and disconnect the negative battery cable to prevent electrical spikes.

2. 2

   Clean and Repair Wiring

   If DEF fluid contamination or wire chafing was found during diagnostics, clean the connectors with electronic contact cleaner. Splice and heat-shrink any damaged wires in the SCR harness.

3. 3

   Replace the Sensor/Pump Module

   If the sensor is internally shorted, replace the DEF pressure sensor. Note: On many Bosch Denoxtronic systems used by New Holland, the pressure sensor is integrated into the DEF Pump Supply Module and cannot be serviced separately; the entire pump must be replaced.

4. 4

   Reassemble and Prime

   Reconnect all harnesses. Reconnect the battery.

5. 5

   Clear Codes

   Use the New Holland Electronic Service Tool (EST) to clear the DCU 19037 and P204D fault codes.

6. 6

   System Test

   Run a forced DEF dosing test or SCR system leak test via the EST to ensure the pump builds correct pressure and the 5V reference circuit remains stable.