U0001

High Speed CAN Communication Bus

Communication network (CAN bus) Generic OBD-II High

What it means

U0001 is a general fault on the high-speed CAN communication bus — the network the vehicle's control modules use to talk to each other. It usually points to a wiring short or open, a bad connector, or a module dragging down the bus. Because so many systems depend on this network, symptoms range widely, from a cluster of warning lights to no-start, stalling, or limp mode, so it should be diagnosed promptly.

High

Can I keep driving? Depends — a healthy high-speed CAN bus is essential; faults can range from a few warning lights to no-start, stalling, or limp mode as modules lose contact. Treat as urgent.

Real-world scan data

Seen in

4,955

scans in the past year

Found in

0.8%

of scans

1.4%

of scans that found faults

Appears alongside · share of U0001 scans

U3003in 56.3% of scans

C1050in 36.1% of scans

C0031in 33.6% of scans

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

Common symptoms

What you'll notice

Multiple, unrelated warning lights at once
No-start, stalling, or intermittent running
Dead or erratic gauges and displays
Reduced power / limp mode
Features like ABS, traction control, or cruise disabled

Common causes

Most likely first

Wiring fault on CAN High/Low (shorted together, to power, or to ground, or an open)Likely
Corroded, backed-out, or damaged connector on the busCommon
A failed module dragging down (loading) the busCommon
Missing or wrong CAN terminating resistorLess often
Poor power or ground to a bus-connected moduleLess often

How to diagnose & fix

Work through it in order

Scan all modules and note which ones can't be reached — that narrows the fault.
Inspect the CAN High/Low wiring and connectors for shorts, opens, and corrosion.
Measure bus resistance at the diagnostic connector — roughly 60 ohms is normal.
Disconnect modules one at a time to find one that's loading down the bus.
Repair the wiring or replace the faulty module, then clear and re-test.

FAQ

Quick answers

Is it safe to drive with U0001?+

Treat it as urgent. A CAN bus fault can knock out multiple systems at once and may cause a no-start, stall, or limp mode. Have it diagnosed before relying on the vehicle.

Can I just clear U0001?+

Clearing it won't fix a wiring or module fault — it will return, often immediately. The bus itself must be diagnosed and repaired.

Read & clear U0001 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX