U0023
Low Speed CAN Communication Bus (+) High
Communication network (CAN bus)
Generic OBD-II
Medium
What it means
U0023 means the voltage on the low-speed CAN "high" (+) wire has risen above its normal range. The low-speed bus links body and comfort modules — lighting, climate, doors, displays — so a voltage-high fault, typically from a wire shorted to power or a failing module, garbles their communication. The engine usually still runs, but accessory and warning features can behave erratically.
Medium
Can I keep driving? Usually yes — the low-speed bus carries body and comfort features, so the engine normally runs, but affected accessories and warning systems may act up until it's fixed.
Common symptoms
What you'll notice
- Body and comfort features glitch or stop (lighting, climate, door/seat modules)
- Warning lights on for systems that share the low-speed network
- Message-center or accessory errors that come and go
- Several communication codes stored across different modules
Common causes
Most likely first
- CAN-high (+) wire shorted to a higher-voltage circuit or to battery powerLikely
- Chafed, pinched, or corroded bus wiring or a faulty connectorCommon
- A failing module biasing the bus voltage highCommon
- Poor ground on a networked module, raising its bus voltageLess often
- Water intrusion in a connector or moduleLess often
How to diagnose & fix
Work through it in order
- Scan all modules and record every stored code — the spread shows which part of the low-speed bus is affected.
- Inspect the low-speed CAN wiring and connectors for chafing, corrosion, or moisture.
- Measure CAN-high/low voltage against spec to find the short-to-high.
- Check module grounds; a bad ground can push a module's bus voltage up.
- Disconnect suspect modules one at a time, then repair wiring or replace the faulty module and re-test.
FAQ
Quick answers
Is it safe to drive with U0023?+
The car usually still drives because this bus handles body and comfort systems, not the engine directly. Even so, warning and convenience features may be unreliable, so get it looked at.
Can I just clear U0023?+
It clears, but a genuine short or failing module brings it right back. Trace and repair the fault first.
Related codes
Often seen with U0023
Read & clear U0023 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