Massey Ferguson 521000.08 – Engine ECU (AGCO SISU POWER EEM4): DEF pump temperature signal duty cycle in failure range

The Engine Control Unit is receiving a temperature signal from the Diesel Exhaust Fluid (DEF) pump's internal temperature sensor, but the signal's duty cycle is outside the acceptable operational parameters. This typically points to a failed internal temperature sensor, a damaged wiring harness, or a failing DEF supply module.

• 4710
• 7724S
• 5712SL
• Interim Tier 4 (2012-2015)
• 7722
• 7722S
• 7615
• 5613
• 5713SL
• 7720S
• 7716
• 7718
• T4
• 7715
• 5710SL
• 7726
• 7616
• 7618
• 5608
• 4708
• 7619
• 7626
• 7726S
• 7624
• 4707
• 4709
• 5711SL
• 7614
• 7718S
• 5610
• 7620
• 7719
• 7714
• 7716S
• T4 (2015-2021)
• 5612
• 7622
• 7720
• Tier 4 (2015-2021)
• 5611
• 7715S
• 5609
• 7724
• Massey Ferguson tractors powered by AGCO SISU diesel engines (Tier 3b, Tier 4i, and Tier 4 Final)

1. 1

   Inspect the wiring harness and connectors between the DEF pump (supply module) and the Engine ECU for corrosion, water intrusion, bent pins, or wire chafing.

2. 2

   Connect a diagnostic service tool (such as the AGCO EDT) to monitor live DEF pump temperature data for erratic, pegged, or missing values.

3. 3

   Back-probe the DEF pump temperature sensor signal wire to verify the duty cycle with a multimeter or oscilloscope.

4. 4

   Check for related codes such as SPN 521000 FMI 2, which further confirms a sensor or module failure.

1. 1

   Preparation

   Turn off the machine, remove the key, and disconnect the battery to prevent electrical shorts. Clean the area around the DEF pump thoroughly to prevent dirt from contaminating the sensitive SCR system.

2. 2

   Disconnect Electricals

   Unplug the main electrical harness connector from the DEF pump.

3. 3

   Disconnect Fluid Lines

   Carefully disconnect the DEF suction, pressure, and return lines. Note: These are often electrically heated lines (tube heaters). Handle the connectors gently so you do not break the heating elements or the restrictor valves.

4. 4

   Remove the Pump

   Unbolt the DEF pump module from its mounting bracket and remove it from the machine.

5. 5

   Install the New Pump

   Mount the new Bosch DNOX 2.2 DEF pump to the bracket and secure the bolts.

6. 6

   Reconnect

   Reconnect the fluid lines, ensuring the quick-connect fittings click securely into place. Reconnect the electrical harness.

7. 7

   Filter Maintenance

   Replace the AdBlue/DEF main filter, as the standard service interval is every 500 running hours.

8. 8

   Finalize

   Reconnect the battery. Use the AGCO EDT diagnostic tool to clear the fault codes. Run a system prime/dosing test to verify that the temperature signal is now reading correctly and that there are no fluid leaks.