Massey Ferguson 521002.31 – Engine Control Unit (ECU): SCR Heating Issue SCR System Shutdown (ECU)

This code indicates a critical failure within the Selective Catalytic Reduction (SCR) heating system, forcing the system to shut down to prevent damage or because it cannot operate correctly. The DEF/AdBlue fluid must be heated to prevent freezing and crystallization in cold temperatures. When the heating system fails (often due to excessive temperature, relay failure, or wiring issues), the SCR system shuts down, which will eventually lead to engine power derates and a limp-home mode.

• 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
• 6600 Series
• 7600 Series
• 8600 Series
• 8700 Series

1. 1

   Inspect the wiring harness and connectors for the DEF heating system for cracked insulation, rub points, and corrosion.

2. 2

   Test the AdBlue/DEF heating main relay for short circuits to +12V or open circuits.

3. 3

   Inspect the insulated supply and return heated lines for kinks, rub points, and nicked O-rings.

4. 4

   Verify AdBlue/DEF quality and inspect the tank for dirt, diesel, or water contamination.

5. 5

   Scan ECU fault history and test sensor voltages to isolate the tank heater element, heated lines, or control valve.

1. 1

   Disconnect Power

   Disconnect the batteries, starting with the negative (-) terminal.

2. 2

   Prepare for Fluid Loss

   Put a drain pan into place beneath the SCR/DEF pump and valve area.

3. 3

   Disconnect Electricals

   Unplug the electrical connector(s) from the heating system solenoid valve or heater element.

4. 4

   Remove Lines

   Remove the retaining clamps and carefully disconnect the heated pipes/lines.

5. 5

   Replace Component

   Swap out the faulty heater valve, relay, or heated line.

6. 6

   Reassembly

   Reconnect the pipes, tighten the nuts/clamps to specification, and plug the electrical connectors back in.

7. 7

   Restore Power & Clear Codes

   Reconnect the battery, clear the fault codes from the ECU using a diagnostic tool, and run the tractor to verify the SCR system primes and heats correctly without shutting down.