Massey Ferguson E521001.03 – Engine Control Unit (ECU): High Voltage Issue With DEF Heater Relay Latching Supply Voltage (ECU)

The DEF heater relay circuit is experiencing a voltage that is above normal, which typically means the DEF heater relay or its cable is shorted to the battery (high source).

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

1. 1

   Stop the engine and let it cool completely before starting work. Do not start the engine during the service procedures.

2. 2

   Check the DEF heater relay connectors for any debris or water ingress, which can cause electrical shorts.

3. 3

   Check for any damaged or loose machine earths (grounds) and inspect the connector pins for corrosion or damage.

4. 4

   Test the DEF heater relay cable/harness to confirm if there is a short circuit to the battery (high voltage source).

1. 1

   Ensure the tractor is turned off, the key is removed, and the engine/exhaust system has cooled down.

2. 2

   Locate the DEF Heater Relay.

   Often designated as relay K68 or K22 in AGCO/Massey schematics depending on the exact model.

3. 3

   Disconnect the relay and inspect the wiring harness leading to the Aftertreatment ECU.

4. 4

   Clean out any water or debris found inside the connector housings.

5. 5

   If the multimeter diagnostic confirms a short to the battery in the wiring harness, repair or replace the damaged section of the DEF heater relay cable.

6. 6

   If the harness is intact but the relay itself is internally shorted, replace the DEF Heater Relay with a new OEM unit.

7. 7

   Clear the DTC codes using a diagnostic tool and cycle the key to ensure the code does not return.