Case IH 3660 – ENGINE (EDC - Electronic Diesel Control): Battery voltage: Power stage diagnosis could be disabled due to low Battery voltage

The Engine Control Unit (ECU) has detected that the system voltage has dropped below the minimum operating threshold (typically below 11.5V). Because the voltage is too low, the ECU is forced to disable its "power stage diagnostics"—meaning it temporarily loses the ability to monitor its own output circuits (like injectors and actuators) for faults.

• skid steer
• Maxxum Series Tractors
• Puma Series Tractors
• Farmall Series Tractors
• Magnum Series Tractors
• Case IH Skid Steer Loaders (SSL)
• Compact Track Loaders (CTL)

1. 1

   Perform a static battery test using a multimeter with the machine off (should read 12.4V to 12.6V)

2. 2

   Perform a battery load test to ensure the battery isn't dropping voltage excessively under demand

3. 3

   Test the charging system by starting the engine and measuring voltage across the battery terminals (alternator should output 13.5V to 14.5V)

4. 4

   Visually inspect the battery terminals, main ground straps, and the wiring harness leading directly to the EDC for corrosion, looseness, or chafing

5. 5

   Check the specific fuses and power relays that feed the Engine ECU to ensure there is no voltage drop across a corroded fuse leg or failing relay contact

1. 1

   Clean Connections

   Disconnect the negative battery cable, followed by the positive. Use a wire brush to thoroughly clean the battery posts and cable terminals. Reconnect and tighten securely.

2. 2

   Replace Battery (If Applicable)

   If the battery failed the load test or has a dead cell causing voltage to plummet during operation, remove the battery hold-downs and install a new battery.

3. 3

   Replace Alternator (If Applicable)

   If the charging system test showed low or no output (and the drive belt is properly tensioned), disconnect the battery, remove the serpentine/drive belt, disconnect the alternator electrical connections, and unbolt the alternator. Install the new alternator and re-tension the belt.

4. 4

   Repair Wiring

   If the battery and alternator are healthy but voltage at the EDC is low, trace the wiring harness from the battery to the EDC. Cut out and splice any damaged wires using weather-sealed heat-shrink connectors.

5. 5

   Clear Codes

   Re-establish power, turn the key to the ON position, and use a CNH Electronic Service Tool (EST) or compatible diagnostic scanner to clear the 3660 fault code.

6. 6

   Test Run

   Start the machine and operate it under load to verify the code does not return.