New Holland 1903 – UCM: UCM Supply Voltage Below Operational Limit

The Universal Control Module (UCM) has detected that its incoming electrical supply voltage has dropped below the operational limit required for proper functioning. This low voltage condition indicates a problem with the power supply to the UCM and can lead to a wide range of erratic machine behaviors, including the logging of multiple 'ghost' fault codes.

• L213
• L215
• L216
• L218
• L220
• L221
• L223
• L225
• L230
• C227
• C232
• C238
• Roll-Belt 450
• Roll-Belt 460
• Roll-Belt 550
• Roll-Belt 560
• BigBaler 230P
• BigBaler 230S
• BigBaler 330P
• BigBaler 340R
• BigBaler 340S
• SR130
• SR160
• SR175
• SR200
• SR210
• SR220
• SR250
• SV185
• SV250
• SV300
• TR320
• TV380

1. 1

   Check battery voltage and charging system output to ensure they are within specifications

2. 2

   Inspect all related fuses and relays, including ground fuses for controllers and relays located in the battery box

3. 3

   Examine the wiring harness connected to the UCM for damage, corrosion, abrasion, or loose connections, focusing on main power and ground

4. 4

   Monitor the electrical system while operating the machine to check for intermittent voltage drops

1. 1

   Confirm fault code

   Use a diagnostic tool to confirm fault code 1903 is active and note any other related active fault codes.

2. 2

   Address basic electrical issues

   Clean and tighten battery cables and connections. Replace the battery or charging system components if they failed the initial diagnostic tests.

3. 3

   Repair wiring and connectors

   Repair or replace any damaged wiring harness sections or connectors. Ensure all connections to the UCM are secure and free of corrosion.

4. 4

   Test UCM power supply

   Using a wiring diagram, test for appropriate voltage directly at the UCM's power supply and ground pins to isolate the issue to the harness or the module.

5. 5

   Clear fault codes

   After performing repairs, clear the fault codes using a diagnostic tool and operate the machine to ensure the fault does not return.

6. 6

   UCM Replacement

   If all other possibilities have been exhausted and the UCM is still reporting low voltage, the UCM itself may be faulty and require replacement. Note that a new UCM may need to be programmed or flashed by a dealer before use.