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Home / DTC / C1666 — Initiator supply short circuit to 12V OR Open circuit

C1666 — Initiator supply short circuit to 12V OR Open circuit

Detailed page for trouble code C1666.

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Code

C1666

HYUNDAI C — Chassis

Initiator supply short circuit to 12V OR Open circuit

Brand: HYUNDAI
Type: C — Chassis
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Page language: EN

Causes

  • Short to battery 12 V on the initiator supply circuit
  • Open circuit (broken wire, disconnected connector, or poor contact)
  • Corroded or damaged connector pins at initiator or airbag ECU
  • Failed initiator (pyrotechnic element or internal wiring)
  • Damage to wiring harness (chafing at hinge, crash damage, rodent chew)
  • Poor or missing ground related to the SRS circuit

Symptoms

  • SRS / airbag warning lamp illuminated on instrument panel
  • Possible disablement of airbag deployment (system fault)
  • Diagnostic trouble code C1666 stored in airbag ECU
  • Intermittent SRS lamp if contact is intermittent
  • No deployment during airbag test (do not intentionally deploy)

What to check

  • Verify the exact DTC(s) and freeze-frame data with an OBD-II / scan tool that supports Hyundai SRS codes
  • Check battery voltage and ground integrity before diagnosis
  • Visually inspect related harnesses and connectors for damage, corrosion, pin push-out, or water ingress (seat belt pretensioner, airbag modules, impact sensors, clockspring/steering column if applicable)
  • Inspect common wear points (door hinge, seat rails, under-seat area) and any areas of previous body repair
  • Measure resistance (ohms) across initiator connector per manufacturer specification with battery disconnected
  • Probe for unintended 12 V on the initiator circuit with ignition ON and compare to expected values

Signal parameters

  • Initiator coil resistance: should be a low resistance value within manufacturer spec (measure with battery disconnected). Open circuit = very high/OL.
  • Supply voltage at initiator supply pin with ignition ON: normally near battery voltage when supply is intended; a short to 12 V may show battery voltage on a control line that should not be powered.
  • Control/output pin at airbag ECU: should match manufacturer expected logic (use wiring diagram); short to 12 V will present battery voltage on that pin when it should be low or disconnected.
  • Continuity between initiator and airbag ECU: low resistance; no continuity indicates open circuit.
  • Short-to-battery check: low resistance between initiator supply and battery + indicates a short.

Diagnostic algorithm

  1. Safety first: Disable SRS power by disconnecting the negative battery terminal and wait the manufacturer-recommended time (commonly 10 minutes or specified interval) to allow system capacitors to discharge.
  2. Use a qualified scan tool to read all SRS codes and freeze frame data; note any additional codes that could be related.
  3. Perform a careful visual inspection of connectors, wiring, and harness routing for damage, corrosion, pin discoloration, or signs of heat or abrasion. Pay special attention to seatbelt pretensioner connectors, seat rails, door hinges, steering column/clockspring, and impact sensor locations.
  4. With battery still disconnected, measure resistance across the initiator (at the module/connector). Compare to manufacturer specification. An open (OL) indicates an open circuit; a very low or shorted reading to chassis ground or battery + indicates a short.
  5. Reconnect battery for voltage tests (only as needed). With ignition ON (engine off), back-probe the initiator supply and control pins and verify voltages against expected values from wiring diagrams. A steady ~12 V on a pin that should be low indicates a short to 12 V.
  6. If a short to 12 V is indicated, isolate sections of the harness by disconnecting connectors and rechecking for the short to find which segment is shorted. Repair or replace the damaged section.
  7. If an open circuit is indicated, trace continuity from the airbag ECU to the initiator to locate the break. Repair wiring or connectors as required.
  8. Check connector pin condition; clean, repair, or replace corroded or damaged connectors and terminals. Use proper crimping and seals for SRS circuits.
  9. If wiring and connectors are good but resistance/short persists, consider replacing the initiator (pretensioner or airbag module) per manufacturer procedures.
  10. After repairs, clear codes with a scan tool, reconnect battery, and verify that the SRS lamp extinguishes and that no new codes are present. Perform any required system resets or calibration per manufacturer.
  11. If codes return after repair, consult wiring diagrams and consider replacing the airbag ECU or seeking manufacturer-level diagnostic support.

Likely causes

  • Damaged harness in door hinge, seat rail, or sub-harness causing short or open
  • Connector pin pushed out, bent, or corroded at the seatbelt pretensioner or airbag module
  • Faulty pretensioner/airbag initiator (internal open or short)
  • Poor repair splice or aftermarket accessory accidentally connected to SRS circuit
  • Short due to metal contact with harness after collision or body work

Fault status

⚠️ Status
Initiator supply short to 12V or open circuit detected — SRS/airbag system fault stored (C1666). Airbag warning lamp illuminated; system may be disabled until repaired.
🔴 Repair difficulty: Hard
⏱️ Diagnostic time: 1-3 hours

Similar codes

C1665 C1667 C1601 C1600 C1700
371

Browse 371 HYUNDAI manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

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