U0020

Low Speed CAN Communication Bus Performance

Q: Is it safe to drive with U0020?

Generally yes — the low-speed bus carries comfort and convenience systems, not the engine, but some features and alerts may not work, so get it diagnosed soon.

Q: Can I just clear U0020?

Clearing hides it briefly, but it comes back until the bus wiring or failing module is repaired.

Network / communication Generic OBD-II Medium

What it means

U0020 means the low-speed CAN network — the bus that ties together convenience and comfort modules like locks, lighting, audio, and climate control — isn't performing to spec. Communication is degraded or unreliable, usually from wiring damage, a poor connector, or one module disrupting bus traffic. The engine normally keeps running, but expect warning lights and features that come and go.

Medium

Can I keep driving? Usually yes — the low-speed bus handles convenience and comfort modules rather than the engine, so the car drives but some features and warning systems may misbehave.

Real-world scan data

Seen in

scans in the past year

Found in

<0.1%

of scans

<0.1%

of scans that found faults

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

Warning lights on with no obvious single failure
Convenience features glitchy — locks, windows, lighting, audio, or HVAC
Modules slow to respond or dropping off the scan tool
Intermittent faults that change with temperature or vibration

Common causes

Most likely first

Corroded, chafed, or broken low-speed CAN wiringLikely
Poor connector contact or water intrusion at a moduleCommon
A single failing module degrading bus trafficCommon
Failed terminating resistor on the busLess often
Software or configuration mismatch after a module or battery serviceLess often

How to diagnose & fix

Work through it in order

Scan every module and record which report bus performance faults or drop off; the shared segment points to the problem area.
Inspect low-speed CAN wiring and connectors for corrosion, chafing, and water, especially in doors and kick panels.
Measure bus voltage and resistance against spec to confirm an open, short, or bad resistor.
Isolate a chatty or dead module by disconnecting suspects one at a time.
Repair the wiring or replace the failing module, then clear and re-test.

FAQ

Quick answers

Is it safe to drive with U0020?+

Generally yes — the low-speed bus carries comfort and convenience systems, not the engine, but some features and alerts may not work, so get it diagnosed soon.

Can I just clear U0020?+

Clearing hides it briefly, but it comes back until the bus wiring or failing module is repaired.

Read & clear U0020 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