Massey Ferguson EE520200.16 – Engine Control Unit (ECU): High Battery Voltage Detected (ECU)

System voltage exceeds the normal operating threshold (typically above 15.5V while the engine is running). This is almost always indicative of an overcharging condition caused by a failed internal voltage regulator within the alternator.

• 7614
• 7615
• 7616
• 7618
• 7619
• 7620
• 7622
• 7624
• 7626
• Interim Tier 4 (2012-2015)
• 4707
• 4708
• 4709
• 4710
• 5608
• 5609
• 5610
• 5611
• 5612
• 5613
• 5710 SL
• 5711 SL
• 5712 SL
• 5713 SL
• 6614
• 6615
• 6616
• 7714 to 7726S
• 8727 to 8740

1. 1

   Live Voltage Test: Start the engine and use a multimeter to measure the voltage directly across the battery terminals. A healthy charging system should read between 13.5V and 14.5V. If the reading is consistently above 15.5V, the alternator is overcharging.

2. 2

   Wiring Inspection: Inspect the wiring harness between the alternator, the battery, and the ECU. Look for any shorts to power or damaged insulation that could be feeding unregulated voltage to the ECU sensors.

3. 3

   Battery Load Test: Test the battery itself. While rare, a severely internally shorted battery can occasionally cause the alternator's regulator to overcompensate.

1. 1

   Disconnect Power

   Turn off the ignition and disconnect the negative (-) battery cable to prevent short circuits and electrical damage.

2. 2

   Remove the Drive Belt

   Locate the belt tensioner, relieve the tension, and slip the serpentine/drive belt off the alternator pulley.

3. 3

   Disconnect Wiring

   Remove the protective boot on the back of the alternator and unbolt the main B+ power cable. Disconnect the electrical regulator harness plug.

4. 4

   Remove Alternator

   Remove the upper and lower mounting bolts securing the alternator to the engine bracket. Carefully extract the heavy alternator from the engine bay.

5. 5

   Install New Alternator

   Position the replacement alternator and hand-thread the mounting bolts. Torque the bolts to the manufacturer's specifications.

6. 6

   Reassembly

   Reconnect the electrical harness and securely fasten the B+ power cable. Route and reinstall the drive belt, ensuring it is seated correctly on all pulleys.

7. 7

   Verify Repair

   Reconnect the negative battery cable. Start the tractor and use a multimeter to verify that the charging voltage is now stable (around 14V).

8. 8

   Clear Codes

   Use a compatible diagnostic scan tool to clear the EE520200.16 DTC from the ECU memory.