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Home / DTC / C120B15 — LED Right Circuit Short to Battery or Open

C120B15 — LED Right Circuit Short to Battery or Open

Detailed page for trouble code C120B15.

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Code

C120B15

HYUNDAI C — Chassis

LED Right Circuit Short to Battery or Open

Brand: HYUNDAI
Type: C — Chassis
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Right-side LED lamp module failed (internal short or open)
  • Wiring shorted to battery positive (pin contacting constant 12V)
  • Open circuit / broken wire between BCM (or lamp controller) and LED
  • Corroded, bent, or poorly seated connector or terminal
  • Blown fuse or fusible link for the lighting circuit
  • Faulty Body Control Module (BCM) or LED driver output

Symptoms

  • Right-side LED (tail, brake or turn lamp depending on circuit) not lighting or not functioning correctly
  • Right LED may be stuck on (if shorted to battery) or completely off (if open)
  • Related dash warning lamp or message illuminated
  • Intermittent operation or flickering of the right LED
  • Other lighting functions on same circuit may be affected

What to check

  • Use a scan tool to read and record freeze frame and stored data for C120B15 and related codes
  • Visually inspect right lamp assembly, lens, and wiring for damage or water ingress
  • Check connectors for corrosion, bent pins, or poor mating at lamp and BCM
  • Inspect relevant fuses and fusible links for continuity
  • Backprobe lamp connector and measure voltages with lamp switched OFF and ON
  • Measure wiring continuity and resistance between BCM/driver and lamp

Signal parameters

  • Battery voltage: ~12–14.5 V (system nominal) at lamp circuit when power applied
  • Open-circuit: infinite resistance (no continuity) between lamp + and driver ground
  • Short-to-battery: battery voltage present at lamp control pin when it should be 0 V or off
  • LED forward voltage: typically 2–4 V for individual LED elements, module sees ~12 V with current control
  • Control signal: steady or PWM output from BCM/LED driver; check frequency and duty if present

Diagnostic algorithm

  1. Connect a capable scan tool. Read and record C120B15 and any related DTCs. Note freeze-frame and whether the fault is current or historical.
  2. Visually inspect the right lamp assembly, harness, and connectors for damage, corrosion, or moisture. Repair obvious issues.
  3. Verify fuses related to the right-side lighting circuit. Replace any blown fuses only after confirming cause.
  4. With ignition ON, backprobe the lamp connector: measure voltage at the power pin and control pin with lamp commanded OFF and ON. A voltage present when OFF indicates a short to battery.
  5. Remove the lamp module and bench-test the LED assembly with a known-good 12 V supply or swap with the left-side module (if identical) to confirm module function.
  6. If module tests OK, perform continuity/resistance checks between the lamp connector and the BCM/LED driver output. Look for opens or high resistance.
  7. If a short to battery is suspected, isolate sections of the harness (disconnect connectors) and re-check voltage to find where battery voltage is appearing incorrectly.
  8. Inspect and repair wiring or connectors as required. After repairs, clear codes and perform functional test cycles to confirm repair.
  9. If wiring and lamp are good and the problem persists, test or replace the BCM/LED driver output following manufacturer procedures.
  10. After repair, clear stored DTCs and verify no return of C120B15 during return-to-service test.

Likely causes

  • Damaged LED lamp assembly
  • Connector corrosion or poor contact at right lamp
  • Broken or chafed wiring harness causing open or short
  • BCM/LED driver output fault (less common)
  • Blown fuse protecting the right LED circuit

Fault status

⚠️ Status
C120B15 — LED right circuit short to battery or open. Fault detected in right-side LED lighting circuit (short to battery or open). Diagnostic trouble code stored. Inspect lamp, wiring, connectors, fuses, and BCM/LED driver.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-1.5 hours

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C1201 C1210 C1234 B1234 U0100
371

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