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Home / DTC / B1504 — Right turn indicator warning lamp open circuit

B1504 — Right turn indicator warning lamp open circuit

Detailed page for trouble code B1504.

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Code

B1504

ALFA ROMEO B — Body

Right turn indicator warning lamp open circuit

Brand: ALFA ROMEO
Type: B — Body
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Burned-out or open filament bulb or failed LED lamp at a right-side turn indicator or dashboard warning lamp
  • Open wiring or broken conductor between the lamp(s) and the instrument cluster/BCM
  • Poor or corroded connector or socket contact at bulb or module connector
  • Blown fuse or faulty relay related to exterior/indicator lighting
  • Faulty instrument cluster or body control module (driver circuit/open output)
  • Aftermarket modification or previous repair left circuit open or disconnected

Symptoms

  • Right turn indicator warning lamp (dash) does not illuminate when right turn is signaled
  • Right-side exterior turn signal may not flash or may be inoperative
  • Turn signal indicator may show bulb-out message or lamp-warning on dash
  • Possible asymmetric flashing rate (fast flash) if a bulb is open

What to check

  • Read/record stored fault (B1504) and freeze-frame data with a diagnostic scanner; clear and attempt to re-create
  • Operate right turn signal and confirm which lamps (front/rear/dash) do or do not illuminate
  • Visually inspect bulbs/LEDs, sockets and connectors for corrosion, damage or looseness
  • Check related fuses and relays for continuity and correct installation
  • Measure voltage at the bulb socket with turn signal ON (expect pulsed supply)
  • Check continuity between the instrument cluster/BCM output pin and the lamp socket

Signal parameters

  • Turn-signal output: pulsed supply ~0–12 V when activated (pulse frequency typically ~1–3 Hz; duty varies)
  • Bulb continuity: incandescent filaments commonly show low ohms (typically a few ohms to tens of ohms); open = infinite resistance
  • LED modules: may present higher resistance or internal electronics; lack of expected pulsed voltage at LED input indicates upstream open
  • Module input/monitor circuits: cluster/BCM may monitor load current; open-circuit condition reported when current below threshold

Diagnostic algorithm

  1. Verify the fault: Connect a scan tool, read B1504 confirmation status and any related codes. Note if the code is current, intermittent or historic.
  2. Reproduce: With ignition ON, activate right turn signal. Observe dash warning lamp and exterior right-side lamps; note which lamps are inactive.
  3. Visual & basic checks: Inspect right-side front and rear bulbs/sockets and dash indicator for obvious damage or corrosion. Check related fuses and relays.
  4. Bulb/socket test: Remove the suspect bulb and test continuity with a multimeter. If open, replace the bulb and retest.
  5. Voltage test at socket: Backprobe the lamp socket with turn signal ON. If no pulsed voltage present, suspect open feed or module output issue.
  6. Continuity & harness inspection: With battery disconnected, check continuity between the cluster/BCM output pin and the lamp socket ground/feed. Repair any open or high-resistance sections.
  7. Connector and ground checks: Clean and reseat connectors; ensure good ground return at lamp chassis ground.
  8. Module output test: If wiring and bulbs are good but no output is present, test the instrument cluster/BCM driver using manufacturer procedures. Replace or repair module only after confirming upstream wiring is intact.
  9. Clear codes and road-test: After repair, clear stored codes and operate the turn signal repeatedly to confirm the code does not return.

Likely causes

  • Failed right-side exterior turn lamp or dashboard indicator bulb (most common)
  • Open/loose connector at bulb socket or inline connector in right-side harness
  • Cut/abraded wiring in harness (pinched or damaged by previous repair)
  • Cluster/BCM output transistor or internal connection failed

Fault status

⚠️ Status
Open circuit detected in right turn indicator warning lamp circuit — no load/voltage detected when right turn signal commanded.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

B1503 B1505 B1510 B1200
89

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