New Holland UCM 1521 – UCM: Left Brake Light Actuation: Open Circuit

The control module has detected a break in the electrical circuit responsible for illuminating the left brake light. An open circuit typically means that electrical current cannot flow because the path is physically broken—most commonly caused by a burnt-out bulb, a disconnected plug, or a severed wire.

• L213
• L215
• L216
• L218
• L220
• L221
• L223
• L225
• L228
• L230
• L234
• C227
• C232
• C234
• C237
• C238
• TR270
• SR175

1. 1

   Remove the left tail light lens and visually inspect the bulb filament for a blown bulb

2. 2

   Inspect the wiring pigtail and the main harness connector leading to the left brake light assembly for loose connections, backed-out pins, or corrosion

3. 3

   Ensure the ground wire for the left tail light assembly is securely fastened to the chassis and free of rust

4. 4

   Use a multimeter to check for continuity along the wiring harness from the UCM to the left brake light socket to rule out a severed wire

1. 1

   Prepare machine

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

2. 2

   Locate assembly

   Locate the left rear tail light assembly on the machine.

3. 3

   Remove lens/housing

   Unscrew the retaining hardware to remove the red lens/housing.

4. 4

   Inspect and replace bulb

   Remove the bulb from the socket. If the filament is broken or the glass is dark/cloudy, replace the bulb.

5. 5

   Clean socket contacts

   If the bulb is intact, clean the socket contacts with electrical contact cleaner and apply a small amount of dielectric grease.

6. 6

   Repair wiring harness

   If the wiring harness is damaged, splice in a new repair pigtail or replace the damaged wire section, sealing it with heat-shrink tubing.

7. 7

   Replace tail light assembly

   If the entire assembly is cracked or water-damaged (causing internal failure), replace the whole tail light assembly.

8. 8

   Verify repair

   Reinstall the housing, turn the machine's key to the ON position, and actuate the brakes to verify the light illuminates and the UCM 1521 code clears.