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DTC codes / U03xx · Software and configuration mismatches / U0339

U0339Software Incompatibility With Body Control Module B

U0339 is a network communication fault indicating that the body control module B (BCM-B) has software that is incompatible with another module on the vehicle's communication bus. The computer detected a mismatch in software version, configuration, or calibration between the BCM-B and a related module, preventing them from exchanging data correctly.

SystemNetwork
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyProfessional
AreaSoftware and configuration mismatches

Symptoms you may notice

  • Illumination of the malfunction indicator lamp (MIL) or a body-related warning light
  • Erratic operation of body functions such as lighting, door locks, or windows
  • Intermittent or complete failure of remote keyless entry or push-button start
  • Battery drain or modules that stay awake after the ignition is turned off
  • Often no symptoms besides the warning light, with all accessories working normally

Common causes, most likely first

  1. Aftermarket or incorrect software flashed into the BCM-B during a repair or update
  2. A replacement BCM-B installed without proper programming or configuration to the vehicle
  3. Corrupted configuration data in the BCM-B or a related module after a low-voltage event
  4. A software update applied to one module without the matching update to the BCM-B
  5. Faulty or mismatched BCM-B part number installed from another vehicle
  6. Communication bus wiring issues that cause incomplete software handshakes between modules

How to diagnose and fix it

  1. Connect a scan tool and read all modules for stored codes, software versions, and configuration data
  2. Verify battery voltage and charging system health, then clear codes and recheck after a test drive
  3. Check for aftermarket accessories or recent module replacements that could introduce software mismatches
  4. Perform a software update or reflash of the BCM-B using the manufacturer's latest calibration files
  5. Run the manufacturer's configuration or setup procedure to align the BCM-B with the vehicle's other modules
  6. Inspect communication bus wiring and connectors for damage or corrosion if software steps do not resolve the code
  7. Replace and program the BCM-B only after confirming the original unit cannot be configured correctly

Software mismatches often hide behind good batteries

  • A weak battery or a voltage drop during a module flash can corrupt configuration data and set U0339 without any hardware failure.
  • Many U0339 cases are caused by a used BCM-B from another vehicle that was never properly configured, not by a defective module.
  • The code can appear after a dealer software update to an unrelated module if the BCM-B calibration is not updated to match.
  • Some vehicles store U0339 as a history code after a one-time low-voltage event and never set it again once cleared.
  • A scan tool that can read module software part numbers is more useful here than a basic code reader, because the mismatch is often visible in the version data.

Can I keep driving with U0339?

The vehicle is generally safe to drive because the fault affects body comfort and convenience systems rather than engine or brake control. Avoid relying on features that may behave unpredictably, such as automatic lighting or keyless entry, and have the software mismatch corrected soon to prevent battery drain or module lock-up.

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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