Massey Ferguson E 9172 (3) – Sisu EEM3 (Engine Electronic Management 3): Start relay control, short circuit to BAT+ (lower side)

The engine management system has detected a short circuit to battery voltage (BAT+) on the low side (ground control side) of the starter relay circuit. The ECU normally controls the starter relay by providing a ground path; however, it is inappropriately detecting 12V on this control circuit, preventing the relay from operating correctly.

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

1. 1

   Verify the battery is fully charged and connections are tight, as low voltage can sometimes cause erratic relay behavior.

2. 2

   Visually inspect the harness between the ECU and the relay panel for chafing, pinched wires, or melted insulation that could cause the cable to contact a battery voltage source.

3. 3

   Disconnect the starter relay and probe the low-side control wire (the pin connecting back to the ECU) for voltage with the key ON. If 12V is present, there is a short to power in the wiring harness.

4. 4

   Test the starter relay itself for internal shorts between the coil pins and the high-current power pins.

1. 1

   Disconnect Power

   Disconnect the negative battery terminal to ensure safety while working on the electrical system.

2. 2

   Repair the Harness

   If your multimeter testing revealed 12V on the ECU ground-control wire, trace the wire loom back toward the ECU. Locate the damaged section where it is rubbing against a power wire. Repair the wire using proper soldering and heat-shrink tubing, and re-loom the harness.

3. 3

   Replace the Relay

   If the wiring tests fine but the relay is internally shorted, remove the old relay from the fuse/relay panel and install a new OEM replacement.

4. 4

   Reassemble and Clear Codes

   Reconnect the battery. Turn the ignition key to the ON position. Use the WinEEM3s Service Tool (or the tractor's onboard diagnostic display) to clear the fault code.

5. 5

   Test

   Attempt to start the tractor to verify the repair and ensure the code does not return.