U0016
Medium Speed CAN Communication Bus (-) Low
Communication network (CAN bus)
Generic OBD-II
Medium
What it means
U0016 means the CAN-low (negative) wire of the medium-speed communication bus is reading below its normal voltage, usually from a short or a failing module. This bus lets control modules talk to each other, so a fault here can make several modules drop offline at once and trigger unrelated warning lights.
Medium
Can I keep driving? Usually drivable, but a bus fault can knock several modules offline at once — expect warning lights and possibly reduced features until it's fixed.
Common symptoms
What you'll notice
- One or more warning lights on (check-engine, ABS, airbag, or others)
- Modules that share the medium-speed CAN bus stop responding to a scan tool
- Intermittent electrical features that drop out and return
- In some cases reduced functions or limp behavior if a key module loses data
Common causes
Most likely first
- Short to ground on the CAN-low wire, pulling bus voltage below normalLikely
- Chafed, pinched, or corroded CAN bus wiring or connectorsCommon
- A failing module dragging the bus voltage downCommon
- Water intrusion or corrosion at a connector or splice packLess often
- Weak battery or low system voltage setting spurious network codesLess often
How to diagnose & fix
Work through it in order
- Scan every module and note which ones are unreachable — that maps where on the bus the fault is.
- Check battery voltage and charging; correct low voltage, then clear and re-test, as weak power sets false U-codes.
- Inspect the medium-speed CAN wiring and connectors for chafing, corrosion, or water intrusion.
- Measure CAN-low to ground and CAN bus resistance to locate the short.
- Isolate modules one at a time to find a unit pulling the bus down; replace the confirmed faulty module or repair the wiring.
FAQ
Quick answers
Is it safe to drive with U0016?+
Often yes for short trips, but a bus fault can disable safety systems like ABS or airbags without warning, so have it diagnosed promptly.
Can I just clear U0016?+
You can, but it returns unless the wiring short or failing module is repaired. A weak battery can also set it, so check voltage first.
Related codes
Often seen with U0016
Read & clear U0016 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