U0044
Vehicle Communication Bus B (-) High
Communication / CAN bus
Generic OBD-II
Medium
What it means
U0044 means the (-) line of Vehicle Communication Bus B reads a higher voltage than expected, disrupting the modules that share that bus. Bus B is a manufacturer-defined network, so the exact impact varies — but the abnormal signal can push modules offline, lighting warning lamps and disabling the features those modules control.
Medium
Can I keep driving? Depends on which modules ride Bus B — the car often still drives, but any module on that bus can drop offline, so verify your gauges and safety systems still work.
Common symptoms
What you'll notice
- Several dash warning lights or messages at once
- Modules on Bus B unreachable by a scan tool
- Features tied to those modules inoperative
- Intermittent electrical faults
Common causes
Most likely first
- Bus B (-) wire shorted to a voltage sourceLikely
- Chafed or damaged bus wiringCommon
- Corroded or loose connector on the busCommon
- A failed module pulling the (-) line highLess often
- Water intrusion at a splice or connectorLess often
How to diagnose & fix
Work through it in order
- Scan every module and log the U-codes to map which are offline on Bus B.
- Inspect Bus B wiring and connectors for chafing, a short to power, or corrosion.
- Measure the bus (-) line voltage and resistance against the manufacturer's spec.
- Isolate modules one at a time to find one pulling the line high.
- Repair the wiring or replace the faulty module, then clear and re-test.
FAQ
Quick answers
Is it safe to drive with U0044?+
Often yes, but it depends what's on Bus B for your vehicle. If it affects braking, steering, or the cluster, drive with caution and repair promptly.
Can I just clear U0044?+
It clears but comes right back while the high signal persists. Fix the wiring or module first.
Related codes
Often seen with U0044
Read & clear U0044 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX