Kubota P0606 – Engine Control Unit (ECU): Microprocessor Failure - COP (Computer Operating Properly) / ECM Processor Fault

The Engine Control Unit (ECU) has detected an internal microprocessor error, CPU anomaly, or flash ROM failure.

• L3901
• L3301
• MX4800
• MX5800
• V2403-CR-TE4
• V2607
• V3307
• V3800
• WG972-GL-E3F
• WG3800
• Kohler KDI 1903-2504

1. 1

   Check battery voltage for irregularities, dead cells, or drops due to cold weather

2. 2

   Check for recent voltage spikes, especially if the tractor was recently jump-started

3. 3

   Inspect the charging system to verify the alternator is not overcharging or undercharging

4. 4

   Inspect grounds, fuses, and wiring harness leading to the ECU for shorts or bad connections (Note: Kubota does not approve internal wire harness repairs for this fault)

1. 1

   Stop the Engine

   Turn off the key switch and let the engine cool. Do not attempt to start the engine during the diagnostic procedure.

2. 2

   Test and Charge the Battery

   Disconnect the battery, test its health under load, and fully recharge or replace it if it fails.

3. 3

   Clear the Code

   Because P0606 can be stored as a 'ghost code' after a low-voltage event or a jump-start, use a diagnostic scan tool to clear the code from the panel.

4. 4

   Test Run

   Run the machine through a few cycles. If the code was simply remembering a low-voltage event, it may not return.

5. 5

   Replace or Repair the ECU

   If the battery and wiring are confirmed good and the code immediately returns, the ECU has suffered a permanent internal hardware failure. The ECU must be removed and either sent to a specialized reconditioning service or replaced entirely.

6. 6

   Reprogramming

   If a new ECU is purchased, it will likely require a Kubota dealer to flash/program the unit to match your specific tractor's immobilizer and engine parameters.