New Holland ENG 3660 – EDC (Electronic Diesel Control): Battery voltage: Power stage diagnosis could be disabled due to low Battery voltage

The unswitched battery voltage supplied to the engine controller has dropped below the minimum operating threshold (typically below 10V). Because the voltage is too low, the controller disables its power stage diagnosis (internal H-bridge driver circuits) to prevent logging false actuator faults caused by insufficient voltage.

• T4.75
• T4.85
• T4.95
• T4.105
• T4.115
• T5 Series
• T6 Series
• T6010-T6070
• Skid Steer Loaders (SSL)
• Compact Track Loaders (CTL)
• B110
• B115
• B95B
• D150B
• D85B
• CR9040
• CR9060
• CR9070
• CR9080
• CX8080
• CX8090

1. 1

   Connect the Electronic Service Tool (EST) and verify that fault code 3660 is currently ACTIVE.

2. 2

   Measure the alternator output voltage while the engine is running. If the output is below 10V, the issue is with the charging system (alternator, batteries, or main cables).

3. 3

   Turn the ignition switch OFF, disconnect the main Engine Control Unit (ECU) harness connector (e.g., connector X-012), turn the ignition switch ON, and measure the voltage from the power supply pins (typically pins 1, 3, 5, and 28) to the ground pins (typically pins 2, 4, and 6). The voltage should be approximately 14.5 V.

4. 4

   While monitoring the EST or a multimeter, wiggle the engine wiring harness to reveal any intermittent shorts or open circuits causing voltage drops.

1. 1

   Resolve Charging System Issues

   If the alternator output was low during diagnostics, repair or replace the alternator, check the battery health, and clean the battery terminals. Clear the codes and retest.

2. 2

   Repair Harness/Relays

   If the battery voltage is good but the voltage at the ECU connector is low, trace the wiring harness back to the battery. Inspect the main power relays, inline fuses, and ground straps for corrosion or damage. Repair as necessary.

3. 3

   Replace the EDC/ECU

   If the unswitched voltage arriving at the ECU connector is correct (approx. 14.5V) under load, but the 3660 fault code remains active, the internal power stage of the ECU has failed. Temporarily swap the ECU with a known good unit to confirm. If the fault clears, permanently replace and program the new Engine Control Unit.