Case IH 19803 – DCU (Dosing Control Unit): UREA Tank Temperature not plausible with Pump module temperature - Temp over CAN: SAE J1939 Too many messages Temp sensor connected directly: SRC low - P0600 Serial Communication Link

This code indicates a plausibility error between the temperature reading of the Diesel Exhaust Fluid (DEF/Urea) inside the tank and the temperature reading at the DEF pump module. The system is detecting a 'Source (SRC) Low' condition (often indicating a short to ground or low voltage) on the directly connected temperature sensor. Additionally, the CAN bus network (SAE J1939) is being flooded with too many messages or is experiencing a serial communication link failure (P0600), preventing the control modules from verifying the correct DEF temperature.

• Tier 4a
• Case IH Steiger 350
• Case IH Steiger 400
• Case IH Steiger 450
• Case IH Steiger 500
• Case IH Steiger 550
• Case IH Steiger 600
• Case IH Rowtrac 350
• Case IH Rowtrac 400
• Case IH Rowtrac 450
• Case IH Rowtrac 500
• Case IH Rowtrac 550
• Case IH Rowtrac 600
• Case IH Magnum 180
• Case IH Magnum 200
• Case IH Magnum 220
• Case IH Magnum 240
• Case IH Magnum 250
• Case IH Magnum 290
• Case IH Magnum MX series
• Case IH Puma 150
• Case IH Puma 165
• Case IH Puma 185
• Case IH Puma 200
• Case IH Puma 220
• Case IH Puma 240
• Case IH Maxxum 115
• Case IH Maxxum 125
• Case IH Maxxum 135
• Case IH Maxxum 145
• Case IH Maxxum 150

1. 1

   Inspect the wiring harness between the DEF tank sending unit (DEF head unit), the DEF pump module, and the DCU for chafed wires, shorts to ground, or corroded pins.

2. 2

   Verify the integrity of the SAE J1939 CAN bus lines, as a shorted CAN line can cause 'Too many messages' and P0600 communication dropouts.

3. 3

   Test the DEF tank temperature sensor resistance/voltage (a reading of 0 ohms or a dead short to ground confirms the sensor has failed internally).

4. 4

   Use a diagnostic scan tool to compare live data for 'DEF Tank Temperature' and 'DEF Pump Module Temperature'. If the tank temperature reads an impossible value (e.g., -40°C) while the pump module reads ambient, the tank sensor is faulty.

1. 1

   Disconnect Power

   Turn off the ignition and disconnect the negative battery cable to prevent electrical spikes while working on the CAN bus and DCU circuits.

2. 2

   Access the DEF Tank

   Locate the DEF tank and clean the area around the DEF head unit (sending unit) to prevent dirt from falling into the tank.

3. 3

   Disconnect the Harness

   Unplug the electrical connector from the DEF head unit and the DEF pump module. Inspect the connectors for DEF fluid intrusion (crystallization), which is a common cause of short circuits and CAN bus communication failures.

4. 4

   Clean or Repair Wiring

   If crystallization or corrosion is found in the connector, clean it thoroughly with electronic contact cleaner. If the harness is damaged, repair the wiring.

5. 5

   Replace the DEF Head Unit

   If the wiring is intact but the tank temperature sensor is shorted (SRC low), the DEF head unit must be replaced. Remove the mounting bolts/lock ring securing the DEF head unit, carefully extract the unit from the tank, and install the new DEF head unit with a new gasket/seal.

6. 6

   Reassemble and Clear Codes

   Reconnect all electrical harnesses and the battery. Use a diagnostic tool to clear the 19803 and P0600 fault codes.

7. 7

   System Test

   Turn the key on and monitor the live DEF temperature data to ensure the tank and pump module temperatures are now plausible and matching ambient conditions.