Massey Ferguson E9026 – Engine ECU: Self-test disconnect lines / Self-test cut-off paths

The control module has detected an abnormally high voltage on the internal or external circuits it uses to perform self-diagnostic shutdowns.

• MF 8600 Series
• MF 8650
• MF 8660
• MF 8670
• MF 8680
• MF 8690

1. 1

   Check ECU power supply by verifying battery voltage and alternator output to ensure the system is not overcharging.

2. 2

   Inspect ECU main relays 1, 2, and 3 for shorts to battery positive (BAT+) or ground (EARTH).

3. 3

   Inspect the wiring harness leading to the Engine ECU for any chafing or shorts to battery voltage (BAT+) that could feed high voltage into the self-test circuits.

1. 1

   Connect diagnostic tool

   Connect the AGCO EDT (Electronic Diagnostic Tool) to the tractor's diagnostic port to confirm the E9026 code and check for any accompanying ECU main relay codes.

2. 2

   Test ECU main relays

   Locate the ECU main relays in the fuse/relay panel. Swap or test the relays to rule out a relay that is stuck closed and feeding constant high voltage to the ECU.

3. 3

   Inspect ECU harnesses

   Disconnect the Engine ECU harnesses and check the pins for corrosion, water ingress, or bent pins.

4. 4

   Repair or replace ECU

   If the wiring loom and relays test perfectly, the fault lies internally within the Engine ECU's processor. The ECU will need to be removed and either sent out for reconditioning, re-flashed, or replaced entirely.