Case IH F-168-00 - ECU – Engine Control Module (ECM) or Electronic Control Unit (ECU): Electrical System Voltage : High

The control module monitors the electrical system's power supply voltage. This fault is triggered when the module detects that the battery voltage has exceeded the maximum acceptable operational threshold (for example, exceeding 16.1V on a standard 12V system). The most common underlying condition is an overcharging alternator due to a failed internal voltage regulator, though it can also be triggered if the machine was incorrectly jump-started with a higher-voltage source (like a 24V jump pack on a 12V system).

• MAGNUM AFS Connect
• Farmall
• Maxxum (MX series)
• Puma
• Magnum
• Steiger series
• Axial-Flow series (e.g., 240 series)
• Windrowers
• heavy construction equipment

1. 1

   Live Voltage Test: With the engine running, use a digital multimeter to measure the voltage directly across the battery terminals. Normal charging voltage for a 12V system should be between 13.5V and 14.5V. If the reading is above 16.1V, the system is actively overcharging.

2. 2

   ECU Pin Voltage Test: Check the voltage at the ECU power supply pins to ensure the high voltage is actually reaching the module and that the code isn't being caused by a software glitch or a faulty ECU internal sensor.

3. 3

   Inspect Connections: Check the electrical power supply connections between the alternator, the battery isolator switch, and the battery.

4. 4

   Verify Operating Conditions: Ensure the code is ACTIVE while the engine is running. If the code is stored but not active, inquire if the machine was recently jump-started with an oversized voltage source.

1. 1

   Disconnect Power

   Turn off the engine and disconnect the negative battery cable to prevent electrical shorts.

2. 2

   Isolate the Alternator

   If the diagnostic checks confirmed an overcharging condition (>16.1V), the alternator's internal voltage regulator has failed.

3. 3

   Remove the Alternator

   Relieve tension on the engine drive belt and remove it from the alternator pulley. Disconnect the wiring harness from the back of the alternator, then unbolt and remove the alternator assembly.

4. 4

   Replace or Rebuild

   Depending on part availability and shop preference, either replace the entire alternator assembly or disassemble the back of the alternator to replace the internal voltage regulator.

5. 5

   Reinstallation

   Mount the repaired/new alternator, reconnect the electrical terminals, and reinstall the drive belt, ensuring proper tension.

6. 6

   Test

   Reconnect the negative battery cable. Start the engine and use a multimeter to verify that the charging voltage has returned to the normal 13.5V - 14.5V range.

7. 7

   Clear Codes

   Connect the Case IH Electronic Service Tool (EST) to the diagnostic port and clear the F-168-00 fault code from the ECU memory.