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Home / DTC / U1943 — Fm2 Antenna circuit Open

U1943 — Fm2 Antenna circuit Open

Detailed page for trouble code U1943.

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Code

U1943

HYUNDAI U — Network/User

Fm2 Antenna circuit Open

Brand: HYUNDAI
Type: U — Network/User
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Broken or disconnected antenna coax/wiring
  • Corroded or loose antenna connector
  • Failed antenna amplifier or mast/active antenna assembly
  • Blown fuse or relay supplying the antenna/amplifier
  • Faulty radio/head unit or internal antenna input circuit
  • Poor ground or damaged shield causing open circuit

Symptoms

  • Weak or no FM reception on radio (especially on FM2 band/input)
  • Static, intermittent reception or missing stations
  • Audio/navigation unit shows antenna fault or loses radio signal
  • Possible related radio error codes or loss of antenna control

What to check

  • Visual inspection of antenna, mast (if fitted), and coax for damage or corrosion
  • Inspect/verify connectors at antenna base and head unit for secure fit and corrosion
  • Check fuses and relays related to radio/antenna power
  • Use scan tool to read radio/AVN module for related codes and status
  • Perform continuity/resistance check of coax and wiring from antenna to head unit
  • Measure supply voltage and ground at antenna amplifier connector with ignition ON

Signal parameters

  • Antenna supply voltage (if active antenna): typically ~11–14 V with ignition/accessory ON — verify exact value in service manual
  • Antenna control signal (if present): may be a switched 12 V or logic-level control — check module pinout
  • Continuity between antenna center conductor and radio antenna input: near 0 Ω (short low-ohms) expected
  • Insulation/ground resistance: should be high (no short to chassis), typically > 1 MΩ
  • RF signal level at head unit: expected measurable FM carrier depending on location — low or zero indicates open

Diagnostic algorithm

  1. Retrieve and record freeze frame/data with a scan tool and confirm U1943 is stored; note any additional codes.
  2. Reproduce symptom: attempt FM reception and verify which inputs/bands are affected (FM2 specifically).
  3. Visual inspection: check antenna mast/assembly, coax, connectors at antenna and radio for damage or corrosion; repair visible damage.
  4. Check fuses/relays: verify radio and antenna amplifier fuses are intact and relays operate correctly; replace if blown.
  5. Backprobe/test at antenna connector: with ignition ON, measure supply voltage and ground at the antenna amplifier connector (refer to wiring diagram for pin locations).
  6. Continuity test: disconnect head unit and check continuity of the antenna coax center conductor from antenna to head unit; repair any open wiring.
  7. Check for short to ground: verify shield/coax insulation not shorted to chassis.
  8. Test antenna amplifier: if removable, verify amplifier operation by applying known good supply or substituting a known-good antenna/amplifier where available.
  9. Test head unit input: confirm the head unit antenna input is functional (swap radio/head unit if necessary or check input circuit per service manual).
  10. Repair or replace failed wiring, connectors, antenna assembly, or antenna amplifier as indicated. Clear codes and retest to confirm repair.

Likely causes

  • Open/short in the antenna coax between the antenna and head unit
  • Failed active (powered) antenna or internal amplifier
  • Disconnected or corroded connector at antenna or head unit
  • No supply voltage to antenna amplifier (blown fuse, wiring fault)
  • Faulty radio/module not detecting antenna presence

Fault status

⚠️ Status
FM2 Antenna Circuit Open — No continuity or missing supply detected to FM antenna 2; radio/AVN module unable to receive FM2 signal.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

U1940 U1941 U1942 U1944 U1000
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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