New Holland 3658 – Engine ECU: ECU Power stages – SPI/COM-Errors of the power failure detection of CY320

This fault indicates an internal hardware or communication failure inside the Engine Control Unit (ECU). Specifically, the main processor has lost SPI communication with the CY320 chip, or a power failure was detected at this power stage. The CY320 chip acts as an internal voltage regulator that manages system power and provides 5V/3.3V reference voltages to external engine sensors. While often an internal ECU failure, external electrical issues can force the ECU to shut down this chip to protect itself.

• T6010
• T6050
• T6000 series
• T7000 series
• B95B
• B110B
• B115B
• CR9040
• CR9060
• CR9070
• CR9080
• D85B
• D95B
• D150B
• F-series motor graders

1. 1

   Check battery voltage: Verify the alternator is not overcharging and the batteries are fully charged, as high battery voltage (Code 3659) or low battery voltage (Code 3660) can disable power stage diagnosis.

2. 2

   Inspect ECU power and ground: Check the main wiring harness, fuses, and relays supplying power to the Engine ECU. A voltage drop on the main supply lines can trigger internal power stage faults.

3. 3

   Check for shorted sensors: A severe short circuit in a 5V sensor or a chafed sensor wiring harness shorting to ground can overload the CY320 chip. Disconnect engine sensors one by one to see if the internal ECU fault clears.

1. 1

   Disconnect battery

   Disconnect the machine's negative battery cable.

2. 2

   Disconnect ECU harnesses

   Locate the Engine ECU (typically mounted on the side of the engine block) and carefully disconnect the main wiring harness connectors.

3. 3

   Remove ECU

   Unbolt and remove the ECU from the machine.

4. 4

   Option A (Repair ECU)

   Send the original ECU to a specialized electronics repair facility (such as Bosch Electronic Service or UpFix). They will open the module, desolder the failed CY320 IC, solder a new chip to the board, and bench-test the unit.

5. 5

   Option B (Replace ECU)

   Procure a new or remanufactured ECU.

6. 6

   Install ECU

   Install the repaired or replacement ECU and reconnect the wiring harnesses.

7. 7

   Reconnect battery

   Reconnect the battery.

8. 8

   Program new ECU

   If a new ECU was installed, a dealer technician must connect the New Holland E.A.S.Y. diagnostic tool to flash the module with the correct software payload for your specific machine. (Repaired ECUs retain their original programming).

9. 9

   Clear codes and test

   Clear the fault codes and test run the engine.