Massey Ferguson 521002.03 – Engine Control Unit (ECU): DEF Reverse Flow Solenoid Valve High Voltage (ECU) / DEF pump direction valve high side short circuit to HIGH SOURCE

The engine management system has detected that the high side of the circuit controlling the DEF pump's direction valve (the reverse flow solenoid used to purge the lines when the machine is shut off) is shorted to a high voltage source (battery voltage).

• 7616
• 5612
• 7622
• Interim Tier 4 (2012-2015)
• 7614
• 5611
• 7615
• 5610
• 5613
• 7620
• 5609
• 7618
• 5608
• 7619
• 7626
• 7624
• 7700 Series
• 4700 Series

1. 1

   Inspect the wiring harness from the EEM4 Engine ECU to the DEF Supply Module for chafing, melted insulation, or pinched wires that could cause a short to a 12V power supply.

2. 2

   Check ECU pins K30 (High Side) and K08 (Low Side). Disconnect the harness at the DEF pump and the ECU, then check for continuity between pin K30 and battery positive. Continuity indicates a shorted harness.

3. 3

   Inspect the electrical connector at the DEF pump for water intrusion, corrosion, or bent pins that could bridge the power supply to the solenoid circuit.

4. 4

   If the wiring harness and connectors test good (no short to high source), suspect an internal failure of the reverse flow solenoid inside the DEF pump.

1. 1

   Disconnect Power

   Turn off the ignition and disconnect the tractor's battery to prevent electrical spikes.

2. 2

   Repair Wiring

   If a short was found in the harness during diagnostics, repair the damaged section of the wire leading to ECU Pin K30, seal it with heat shrink, and secure the harness away from heat sources or sharp edges.

3. 3

   Replace the DEF Supply Module

   If the wiring is good, the reverse flow solenoid has likely failed. Relieve any residual pressure in the DEF lines. Disconnect the DEF suction, pressure, and return lines from the pump module. Disconnect the main electrical harness from the pump. Unbolt the DEF pump from its mounting bracket and remove it. Install the new DEF Supply Module and reconnect the fluid lines and electrical connector.

4. 4

   Prime and Clear Codes

   Reconnect the battery. Use an AGCO diagnostic service tool to clear the EEM4 fault codes. Run a DEF system functional test/override to prime the pump and verify that the reverse flow solenoid operates correctly without throwing the high voltage code.