Massey Ferguson 520264.31 – Engine Control Unit (ECU): CY146 error 5 / Reported SPI and COM-Errors of a Cy146

A critical internal hardware failure, specifically a Serial Peripheral Interface (SPI) or communication error within the engine controller's CY146 microchip circuitry.

• 4710
• 7724S
• 5712SL
• 7722S
• 7722
• 5713SL
• 7720S
• 7716
• 7718
• T4
• 7715
• 5710SL
• 7726
• 4708
• 7726S
• 4707
• 4709
• 5711SL
• 7718S
• 7719
• 7714
• 7716S
• T4 (2015-2021)
• 7720
• Tier 4 (2015-2021)
• 7715S
• 7724
• MF 7600 Series
• 7614
• 7618
• 7624
• MF 7700 Series
• MF 8600 Series
• MF 4700 Series

1. 1

   Verify Power and Ground: Check the ECU power supply and ground connections. Voltage spikes, severe drops, or poor grounding can cause internal chip communication errors.

2. 2

   Inspect Connectors: Check the main engine harness connectors at the ECU for moisture ingress, corrosion, or bent pins.

3. 3

   Software Verification: Connect the AGCO Electronic Diagnostic Tool (EDT). Test the original EEM4 unit with the latest software update to ensure a software glitch isn't triggering a false hardware fault.

4. 4

   Cross-Check: If the system is functional but the fault remains active after a software flash, the official AGCO troubleshooting procedure dictates testing with a known-good replacement ECU. If the fault clears, the original ECU is permanently defective.

1. 1

   Connect diagnostic tool

   Connect the EDT device to the tractor and open the diagnostic software.

2. 2

   Save engine log

   Open the "Diagnostic Test" page, select "Save & Upload Engine Log," and save the engine log information to your desktop.

3. 3

   Save IQA codes

   Open the "Calibration" tab, check the Injector Quality Assurance (IQA) codes, and save them for later use.

4. 4

   Deactivate old ECU

   Open "Configuration", select "Engine ECU Replacement", and click start. Click "Continue Step 1" to deactivate the old ECU.

5. 5

   Power down system

   Turn the ignition switch to OFF and wait exactly 2 minutes for the power to completely cut off from the tractor's control units.

6. 6

   Disconnect battery

   Disconnect the battery negative terminal.

7. 7

   Remove old ECU

   Unplug the wiring harnesses from the Engine ECU and unbolt the module from the engine block/bracket.

8. 8

   Install new ECU

   Install the new replacement ECU and reconnect the wiring harnesses.

9. 9

   Reconnect power

   Reconnect the battery and turn the ignition switch to ON. The EDT will automatically read the serial number of the new ECU.

10. 10

    Activate and program new ECU

    Follow the EDT prompts to activate the new unit and write the saved IQA codes and engine logs to the new module. Caution: Do not use a used ECU from another tractor. Doing so can cause engine hour mismatches and immobilizer lockouts.