U0045
Vehicle Communication Bus B (-) shorted to Bus B (+)
Data bus (CAN)
Generic OBD-II
Medium
What it means
U0045 means the two wires of Communication Bus B — CAN-High and CAN-Low — are shorted together. A short between the bus wires collapses the signal and typically stops every module on Bus B from communicating at once, so expect multiple warning lights and several features failing together.
Medium
Can I keep driving? Risky to rely on — a shorted bus can take a whole group of modules offline, disabling their features and lighting up warnings; diagnose before driving much.
Common symptoms
What you'll notice
- Several warning lights on simultaneously
- Multiple modules on Bus B missing from a scan
- Features served by Bus B dead or erratic
- A cluster of lost-communication U-codes
Common causes
Most likely first
- CAN-High and CAN-Low wires shorted together (crushed or pinched harness)Likely
- Water or corrosion bridging two pins in a connectorCommon
- A failed module internally shorting the bus pairCommon
- Damaged connector or spliceLess often
How to diagnose & fix
Work through it in order
- Scan all modules to confirm the whole of Bus B is affected.
- Inspect the Bus B harness for a pinched or crushed section shorting the pair.
- Check connectors for corrosion or moisture bridging the two bus pins.
- Measure resistance between CAN-High and CAN-Low; a near-zero reading confirms the short.
- Disconnect modules one at a time to find an internally shorted unit, then repair wiring or replace the module.
FAQ
Quick answers
Is it safe to drive with U0045?+
Not ideal — a bus-to-bus short can knock out a whole group of modules at once. Get it diagnosed before relying on the car.
Can I just clear U0045?+
It comes straight back while the two wires are shorted. Locate and repair the short first.
Related codes
Often seen with U0045
Read & clear U0045 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