Case IH 17771 (F-7107-16) - ECU – ECU: DEF/AdBlue supply module pump motor - Internal pump duty cycle above maximal limit.

This code indicates that the DEF (Diesel Exhaust Fluid) pump motor is working too hard (its PWM duty cycle has exceeded the maximum allowable threshold) to build or maintain the required fluid pressure in the SCR system. This typically points to a restriction in the DEF supply lines, a severely clogged DEF filter, a fluid leak causing the pump to run continuously, or a failing internal pump motor.

• VESTRUM CVX
• Austoft 9900
• Austoft 9900DA
• Austoft 9000 series

1. 1

   Evaluate the maintenance history to see if the DEF filter is due for replacement, as a clogged DEF filter is the most common cause of a high duty cycle.

2. 2

   Verify the DEF tank has adequate fluid and that the concentration/quality is correct. Inspect all DEF suction and pressure lines for kinks, blockages, or external leaks.

3. 3

   Check for any damaged or loose machine grounds, harness connectors, and pins at the DEF supply module. Look for debris or water inside the connector terminals (often caused by pressure washing).

4. 4

   Connect the diagnostic tool (e.g., PT-Box or dealer EST) and perform a Urea Dosing System Test (UDST) to monitor the pump's pressure buildup and duty cycle.

1. 1

   Preparation

   Ensure the engine is off and the exhaust/SCR system has cooled down. Thoroughly clean the area around the DEF supply module to ensure it is completely free of dried white urea crust and dust before opening the filter cap.

2. 2

   Filter Replacement (Primary Fix)

   Open the DEF filter housing cap. Use the specialized extraction tool (usually included with the filter kit) to carefully pull out the old filter element without scratching the inner walls of the pump housing reservoir. If flushing the external housing face, use only clean distilled water to safeguard the internal high-pressure fluid loops. Install the new DEF filter cartridge and secure the cap.

3. 3

   Module Replacement

   If the pump motor itself is worn out and cannot maintain pressure even with a clean filter, the entire DEF Supply Module must be replaced. Disconnect the electrical harness and DEF lines, unbolt the module from its mounting bracket, and install the new unit.

4. 4

   Post-Repair

   Turn on the ignition switch, use the diagnostic scan tool to clear the DTC (P20C9 / 17771), and run a dosing system test to verify the pump duty cycle has returned to the normal operating range.