B1499

Code

Other B — Body

Lamp Turn Signal Left Circuit Failure

Brand: Other

Type: B — Body

Views: UK: 27 EN: 33 RU: 33

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Page language: EN

Causes

Burned-out or failed left turn signal bulb (incandescent) or LED element failure
Corroded, bent, or damaged bulb socket or connector
Open or shorted wiring between the lamp and the body control module (BCM)
Poor or missing ground at the lamp circuit
Blown fuse or faulty relay protecting the lamp circuit
Faulty turn signal switch or multi-function switch

Symptoms

Left turn signal lamp does not illuminate when signaling left
Left turn signal may flash rapidly or not flash at all
Hazard lights may show same behavior for the left side
Instrument cluster may display a lamp-out warning or DTC present
Intermittent operation of left turn signal (works sometimes)

What to check

Verify customer complaint and note conditions when fault occurs (ignition on, hazards, left signal, speed)
Check if hazard lights activate both sides correctly
Visually inspect left turn lamp, lens, and socket for corrosion, moisture, or damage
Inspect and, if necessary, swap or replace the left bulb with a known-good bulb
Check relevant fuses and turn-signal relay (if applicable)
Scan vehicle for additional DTCs and check BCM/lighting module data/live values

Signal parameters

Supply voltage at lamp terminal: ~11–14 V when circuit is powered
Open-circuit voltage: ~0 V at lamp output when not commanded (depends on module)
Flasher/flash rate: ~1–2 Hz (1–2 flashes per second) for incandescent systems
LED-driven circuits may use PWM: drive frequency can vary (low-frequency flash or high-frequency PWM carrier)
Expected current draw (incandescent): ~0.5–3 A per bulb; (LED): typically
Continuity: low resistance between lamp + terminal and module output when lamp installed; open circuit indicates break

Diagnostic algorithm

Verify complaint: confirm left turn signal function with ignition on and hazard switch; note symptoms and repeatability.
Visually inspect left lamp assembly, lens, socket and wiring for damage, corrosion or moisture; repair obvious damage.
Replace or swap the left bulb with a known-good bulb (or substitute known-good left/right) and retest.
Check fuses and relays for the lighting/turn-signal circuit; replace if blown/defective.
With turn signal commanded ON, measure voltage at the bulb positive terminal and at the socket ground; verify ~12 V and good ground.
If no voltage at socket, trace wiring back: inspect connectors and measure voltage at each connector while commanding the signal.
Perform continuity/resistance test between the lamp connector and the BCM lamp output pin; check for open or high resistance.
Wiggle harness and connectors while commanding the signal to check for intermittent opens/shorts; repair any damaged wiring or terminals.
If voltage toggles appropriately at BCM output but lamp does not illuminate, test current capability (use test lamp or ammeter) to determine short/open or load issue.
If BCM output is absent or abnormal and wiring is confirmed good, check related inputs (turn signal switch) and module grounds/power; consult wiring diagram.
If module is suspected faulty after verifying wiring, follow manufacturer procedures for BCM/module testing and replacement; clear codes and road-test to confirm repair.
After repair, clear DTCs, cycle ignition, and verify proper operation of left turn and hazard functions; monitor for reoccurrence.

Likely causes

Failed bulb or LED (most common)
Corroded/bad socket or loose connector
Open circuit (broken wire) or poor ground at lamp
Blown fuse or faulty relay
Faulty BCM or output driver (less common)

Fault status

⚠️ Status

Left turn signal lamp circuit failure detected (open/short/low load) — left turn lamp may not function correctly. Diagnostic testing of lamp, wiring, and control module required.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.5 hours