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DTC codes / B04xx · Airbags, seats, doors, lights and comfort systems / B0440

B0440Bluetooth Module Fault

B0440 indicates that the body control module (BCM) or a dedicated communication gateway has detected a fault within the Bluetooth module circuit, typically a loss of expected serial data or a power/ground issue. The computer sets this code when the Bluetooth module fails to respond to handshake messages or reports an internal error over the controller area network (CAN) or dedicated serial link.

SystemBody
Code typeGeneric (all makes)
SeverityLow
Fix difficultyIntermediate
AreaAirbags, seats, doors, lights and comfort systems

Symptoms you may notice

  • The Bluetooth system fails to pair with phones or other devices, or the pairing process times out repeatedly.
  • The infotainment screen shows a 'Bluetooth unavailable' or 'Communication error' message, and the Bluetooth icon may be greyed out.
  • Hands-free calling and audio streaming features stop working entirely, even if other infotainment functions operate normally.
  • Often no symptoms besides the warning light, because some vehicles only illuminate a generic body fault indicator without disabling other functions.
  • Intermittent Bluetooth connectivity where devices connect and disconnect randomly, especially over bumps or in hot weather.
  • The Bluetooth module may be completely dead, with no response to any scan tool commands or module wake-up attempts.

Common causes, most likely first

  1. A failed Bluetooth module, often due to internal component degradation from heat or voltage spikes.
  2. Corroded, loose, or damaged wiring and connectors in the Bluetooth module circuit, particularly at the module harness or inline connectors.
  3. A blown fuse or poor ground connection supplying power to the Bluetooth module.
  4. A software or firmware glitch in the Bluetooth module or the body control module that handles its communication, requiring a reflash or reset.
  5. A faulty body control module (BCM) or communication gateway that cannot properly relay messages to the Bluetooth module.
  6. Voltage supply issues such as a weak battery or charging system problems that cause the Bluetooth module to drop offline intermittently.
  7. Water intrusion or physical damage to the module or its wiring, often from a leaking windshield or clogged sunroof drain.

How to diagnose and fix it

  1. Use a scan tool to read all body codes and confirm B0440 is current, then check for related communication codes in other modules to rule out a network-wide issue.
  2. Inspect the Bluetooth module fuse and ground connections, testing for battery voltage at the module connector with the key on.
  3. Perform a visual inspection of the Bluetooth module and its wiring for corrosion, chafing, or loose pins, especially at connectors behind the dashboard or in the trunk.
  4. Disconnect and reconnect the Bluetooth module connector to reseat it, then clear the code and retest to see if the fault returns immediately.
  5. Check for technical service bulletins (TSBs) or software updates for the Bluetooth module and body control module, and apply any available reflash or reset procedure.
  6. If power, ground, and communication lines test good, substitute a known-good Bluetooth module or perform a module swap to confirm the fault follows the module.
  7. After repair, clear all codes, cycle the ignition, and verify that the Bluetooth module communicates and pairs with a device before returning the vehicle.

Before you replace the Bluetooth module

  • A dead battery or low voltage from a failing alternator can cause the Bluetooth module to set B0440 intermittently, so always load-test the battery and charging system before condemning the module.
  • Many vehicles require a specific pairing or reset procedure after battery replacement or module disconnect, and skipping it can leave a false B0440 stored even though the hardware is fine.
  • Corrosion at the module connector is a common hidden cause, especially on vehicles with sunroofs or roof-mounted antennas where water can travel down the harness.
  • The code can be set by a communication timeout rather than a hard module failure, so a simple module reset or software reflash often resolves it without parts replacement.
  • A faulty body control module or gateway can mimic a Bluetooth module fault by failing to wake the module or route messages, so always check for other body codes before replacing the Bluetooth unit.

Can I keep driving with B0440?

The vehicle remains safe to drive because the Bluetooth fault does not affect steering, braking, or engine operation, but you should avoid relying on hands-free calling until repaired. If the code is accompanied by other body or communication codes, have the system diagnosed promptly to rule out a broader electrical issue.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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