Case IH 3660 – Engine Control Unit (ECU) / Electronic Diesel Control (EDC): Battery voltage : Power stage diagnosis could be disabled due to low Battery voltage.

The control module has detected that the system's battery voltage has dropped below a critical operating threshold (typically below 9.0V, which often happens during engine cranking in cold conditions or due to a failing battery). Because low voltage can cause electronic actuators to behave erratically, the ECU temporarily disables its internal power stage diagnosis as a protective measure.

• Puma
• Magnum
• Maxxum
• skid steers
• loaders
• backhoes

1. 1

   Measure the static battery voltage with the machine off (should read between 12.4V and 12.8V)

2. 2

   Monitor the battery voltage while cranking the engine (if voltage drops below 9.0V, batteries are weak or failing)

3. 3

   Check the charging system voltage at the battery terminals with the engine running (should read between 13.5V and 14.5V)

4. 4

   Visually inspect battery terminals, crossover cables (if equipped with dual batteries), and the main chassis ground for heavy corrosion, looseness, or fraying

5. 5

   Check the specific power supply pins at the Engine ECU harness to ensure full voltage is reaching the module without excessive voltage drop

1. 1

   Safety First

   Turn off the machine, remove the ignition key, and engage the parking brake.

2. 2

   Clean Connections

   Disconnect the negative battery cable(s), followed by the positive cable(s). Use a wire brush and battery terminal cleaner to remove all corrosion from the battery posts and cable clamps.

3. 3

   Clean the Main Ground

   Trace the negative battery cable to where it bolts to the chassis or engine block. Remove the bolt, wire-brush the mating surface down to bare metal, and reinstall the ground cable tightly.

4. 4

   Replace Failing Batteries

   If the batteries failed the cranking test or a dedicated carbon-pile load test, replace them. Note: If your machine uses two batteries in parallel, always replace both at the same time to prevent the older battery from draining the new one.

5. 5

   Address the Charging System

   If the running voltage was below 13.5V during your diagnostic checks, inspect the alternator belt for proper tension and wear. If the belt is good, the alternator is likely faulty and must be replaced.

6. 6

   Clear the Code

   Reconnect all components, start the tractor, and use the CNH Electronic Service Tool (EST) or an equivalent diagnostic scanner to clear the inactive 3660 fault code from the EDC memory.