U0015
Medium Speed CAN Communication Bus (-) Open
Data bus (CAN)
Generic OBD-II
Medium
What it means
U0015 means a control module has detected an open (broken) connection on the negative CAN-Low wire of the medium-speed data bus. This is the network that lets modules talk to each other, so an open on this wire can garble or stop communication between the modules that share it — several features can act up at once and warning lights appear.
Medium
Can I keep driving? Often fine for a short trip, but expect warning lights and glitchy features on the affected bus; a fully dead bus can disable systems, so diagnose it soon.
Common symptoms
What you'll notice
- Check-engine or other warning lights on, sometimes several at once
- One or more modules on the bus stop responding to a scan tool
- Intermittent or lost function of features that share the medium-speed bus
- Multiple U-series communication codes stored together
Common causes
Most likely first
- Broken, chafed, or corroded CAN-Low wire on the medium-speed busLikely
- Loose or corroded connector at a module or bus junctionCommon
- Water intrusion into a harness connectorCommon
- A failed module opening or dragging down the busLess often
- Damaged bus terminating resistorLess often
How to diagnose & fix
Work through it in order
- Scan all modules and record every stored U-code to map which part of the bus is affected.
- Check battery voltage and charge — low voltage causes false communication faults.
- Inspect the medium-speed CAN wiring and connectors for damage, corrosion, or water, and repair what you find.
- With the key off, measure resistance across CAN-High/Low; a healthy two-resistor bus reads about 60 ohms.
- Disconnect modules one at a time to isolate a unit that's opening the bus, then retest.
FAQ
Quick answers
Is it safe to drive with U0015?+
Often for a short trip, but communication faults can disable features unpredictably. If warning lights multiply or a system quits, stop and get it checked.
Can I just clear U0015?+
You can, but if the wiring open is still there it returns as soon as the affected modules try to talk again. Fix the circuit first.
Related codes
Often seen with U0015
Read & clear U0015 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