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Home / DTC / B2840 — BT Module Communication Error

B2840 — BT Module Communication Error

Detailed page for trouble code B2840.

33,912codes
59brands
11,451generic
22,461specific
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Code

B2840

HYUNDAI B — Body

BT Module Communication Error

Brand: HYUNDAI
Type: B — Body
Views: UK: 21 EN: 30 RU: 28
AI status
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Page language: EN

Causes

  • Failed or intermittent Bluetooth/hands‑free module
  • Damaged wiring, corroded connectors, or poor pin contact at the module
  • Loss of power or ground to the module (blown fuse, open circuit)
  • Faulty CAN/LIN bus wiring, high bus impedance, or missing termination
  • Software/configuration error or required reprogramming
  • Radio interference or antenna/ground fault affecting module operation

Symptoms

  • Bluetooth pairing/connectivity failures or intermittent operation
  • Hands‑free call functions not working or dropping audio
  • Infotainment errors or warning message about Bluetooth module
  • Stored B2840 code on the vehicle network scan
  • Other modules reporting lost communication or degraded features

What to check

  • Connect a diagnostic scanner and confirm B2840 and any additional network codes; review freeze frame and related U‑codes
  • Visual inspection of BT module connector for corrosion, bent pins, water ingress, or damage
  • Verify fuses and battery feed to the BT module circuit; check ground continuity
  • Check CAN/LIN bus continuity and voltages at the module connector
  • Inspect antenna and antenna ground for damage (if external antenna used)
  • Review OEM technical service bulletins (TSBs) and software updates for the module

Signal parameters

  • Module supply voltage: approx. battery voltage (typically 11–14 V with ignition ON)
  • Module ground: near 0 V continuity to chassis ground
  • CAN bus idle voltages: CAN_H ≈ 2.5–3.5 V, CAN_L ≈ 1.0–2.0 V (differential ~0 V at idle as both sit near mid‑rail)
  • LIN (if used) idle: near battery voltage when idle or per OEM spec
  • Serial/UART signals (if applicable): logic‑level TX/RX activity when module communicating

Diagnostic algorithm

  1. Retrieve freeze frame data and all stored DTCs with a capable scan tool; note related U‑codes or body network errors.
  2. Attempt to clear codes and reproduce; observe if B2840 returns immediately or only under certain conditions.
  3. Inspect module connector and harness for corrosion, damage, water entry, or poor pin contact; wiggle test harness while monitoring codes/communication.
  4. Verify power and ground at the module connector with ignition ON; check relevant fuses and relay operation.
  5. Measure CAN/LIN bus voltages at the module connector; if abnormal, trace the bus for shorts/opens and check terminations (120 Ω across CANH/CANL with key off if accessible).
  6. Use a scope or CAN‑bus logger to observe bus traffic and confirm presence/absence of module frames and bus errors.
  7. If wiring and bus are good, check for available software updates or known issues from OEM; reflash/reprogram module per factory procedure if required.
  8. If module still fails communication after wiring, power, ground, and software checks, consider replacing the Bluetooth/hands‑free module and re‑programming/configuring it to the vehicle.
  9. After repair, clear codes and verify all related systems function; road test and re‑scan to confirm no recurrence.

Likely causes

  • Corroded/loose connector at the BT module
  • Blown fuse or missing battery feed/ground to the module
  • CAN bus short, open or missing reference (other module pulling the bus)
  • Internal failure of the Bluetooth/hands‑free module
  • Module requires software update or incorrect module coding

Fault status

⚠️ Status
B2840 — Bluetooth (hands‑free) module communication error: module not responding or data invalid on vehicle network.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-2.5 hours

Similar codes

U0100 U0073 U0140 U0155 U0121
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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