Case IH 3573 – Engine Control Unit (ENG / EDC) / Dosing Control Unit (DCU): Urea quality and urea warning level 3

The system has detected that the Diesel Exhaust Fluid (DEF / Urea) concentration is outside the acceptable parameters (typically it should be 32.5% urea), or the DEF quality sensor itself is malfunctioning. A Level 3 warning is a severe escalation that will typically induce an engine derate.

• Case IH Magnum Series (235, 260, 290, 315, 340 - Series 4)
• Case IH Steiger & Quadtrac Series
• Case IH Puma and Maxxum Series

1. 1

   Test the DEF Quality: Extract a sample of the DEF directly from the tank and test it using a DEF refractometer. The concentration must be exactly 32.5%.

2. 2

   Inspect the Wiring Harness: Check the wiring harness between the DCU and the DEF tank level/temperature/quality sensor. Look for chafing, corrosion, or disconnected pins.

3. 3

   Check Sensor Resistance & Power: Disconnect the urea fluid sensor harness and inspect the power supply circuit between the ignition switch and the sensor. Verify the resistance across the DCU connector pins and the DEF sensor connector pins.

4. 4

   Check for Accompanying Codes: Look for related DCU codes such as 3577 (DM1DCU SPN1 message - Error in DCU active) or 3581 (Performance limit active) which often accompany a Level 3 derate.

1. 1

   Turn off ignition and disconnect battery

   Turn off the ignition and disconnect the battery ground.

2. 2

   Drain DEF tank

   Drain the DEF tank completely into an appropriate disposal container.

3. 3

   Flush DEF tank

   Flush the tank with distilled water to remove crystallized urea or contaminants.

4. 4

   Replace DEF supply filter

   Replace the DEF supply filter.

5. 5

   Refill DEF tank

   Refill the tank with fresh, high-quality, API-certified DEF (32.5%).

6. 6

   Clear codes and test

   Reconnect the battery, turn the ignition on, and use the CNH Electronic Service Tool (EST) to clear the DCU and Engine DTCs. Observe if the code resets.

7. 7

   Disconnect battery ground

   Disconnect the battery ground.

8. 8

   Disconnect electrical harness

   Disconnect the electrical harness connector from the top of the DEF tank header.

9. 9

   Disconnect lines

   Relieve system pressure and disconnect the DEF suction, return, and coolant heating lines from the header unit. Cap the lines to prevent contamination.

10. 10

    Unscrew locking ring/bolts

    Unscrew the locking ring or mounting bolts securing the DEF header to the tank.

11. 11

    Extract old DEF header

    Carefully extract the old DEF header unit, taking care not to drop debris into the tank.

12. 12

    Install new DEF header

    Install the new DEF header unit with a new OEM base seal/O-ring.

13. 13

    Reconnect lines and harness

    Reconnect the coolant lines, DEF lines, and electrical harness.

14. 14

    Refill DEF tank

    Refill the tank with fresh DEF.

15. 15

    Clear codes and perform system test

    Connect the CNH EST diagnostic tool, clear the 3573 fault code, and perform a system test to verify the sensor is reading the correct urea concentration.