Massey Ferguson 4375.04 – Engine Control Unit (ECU) / Aftertreatment Control Module (ACM): DEF Pump Control Issue / DEF pump motor control signal short circuit to GROUND

The controller has detected that the command circuit for the Diesel Exhaust Fluid (DEF) pump motor has a voltage that is below the normal calibrated range. This typically indicates a short circuit to ground in the wiring harness or an internal short within the DEF pump module itself.

• 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

1. 1

   Disconnect the DEF pump harness connector and visually inspect the sensor harness and connector pins for bent, spread, or corroded terminals.

2. 2

   Perform a circuit isolation test: Turn the ignition ON (engine OFF), clear active fault codes, and recheck. If the code remains active while the pump is disconnected, the short-to-ground is in the wiring harness. If the code goes inactive or changes to an open circuit code, the short is internal to the DEF pump.

3. 3

   Conduct a wiggle test on the ECU/ACM connector and the DEF pump harness while monitoring the live fault code status on a diagnostic tool to locate intermittent shorts in the wiring loom.

1. 1

   Repair Wiring

   If the diagnostic tests point to the harness, locate the chafed or pinched wire causing the short to ground (often found where the harness routes along the frame rail near the exhaust/DEF tank). Splice and repair the damaged wire, or replace the affected harness section.

2. 2

   Repair Connectors

   If pins are corroded or damaged, clean the contacts with electrical contact cleaner and replace the damaged pins/pigtails.

3. 3

   Replace DEF Pump

   If the wiring harness tests perfectly and the short is isolated to the pump itself, remove the DEF lines and electrical connectors from the DEF Supply Module. Unbolt the module from its mounting bracket and install the replacement unit.

4. 4

   System Verification

   Reconnect all components. Clear the fault codes. Run the SCR Airless Dosing System (ADS) self-check routine via the diagnostic tool, or run the tractor under load to verify that the DEF system builds pressure and the code does not return.