OBD2 code U0039: Vehicle Communication Bus B (+) Open
Bus B high-side line is open — broken wire or disconnected.
Detected Root Component
Network Component
Observed Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
Possible Causes
- Wire broken or connector unplugged
- Gateway module routing CAN messages incorrectly
- CAN terminating resistor (120 Ω) drifted out of spec
Tools Required
Interactive Diagnostic
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Parts likely to be the cause (Moteur (général))
Moteur (général)
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Frequently asked questions about code U0039
What does code U0039 mean? ▾
OBD2 code U0039: Vehicle Communication Bus B (+) Open. Bus B high-side line is open — broken wire or disconnected.
What are the symptoms of code U0039? ▾
Code U0039 may cause: Multiple warning lights may illuminate, Affected modules may go into limp mode or shut down, Specific functions inoperative depending on module, Diagnostic tools may show communication faults. The intensity of these symptoms varies depending on the vehicle and driving conditions.
What causes code U0039? ▾
The most common causes of code U0039 are: Wire broken or connector unplugged, Gateway module routing CAN messages incorrectly, CAN terminating resistor (120 Ω) drifted out of spec. A proper OBD2 diagnostic will pinpoint the exact cause.
Is it serious to drive with code U0039? ▾
Yes, code U0039 is critical (Critical). Avoid driving and consult a professional promptly to prevent major damage.
How do I fix code U0039? ▾
Start by reading the code with an OBD2 scanner, then follow the interactive decision tree on this page. Priority causes to check: Wire broken or connector unplugged, Gateway module routing CAN messages incorrectly, CAN terminating resistor (120 Ω) drifted out of spec. Difficulty: Medium · Estimated time: 30-60min.