U0029

Vehicle Communication Bus A Performance

Q: Is it safe to drive with U0029?

Usually, but a degraded bus can intermittently disable features. If safety systems or warning lights are involved, have it diagnosed before relying on the car.

Q: Can I just clear U0029?

You can, but a 'performance' fault means the bus is still communicating poorly — the code returns until the wiring or module problem is fixed.

Communication network (vehicle bus) Generic OBD-II Medium

What it means

U0029 means one of the vehicle's communication buses (bus "A", defined by the manufacturer) is still working but performing poorly — messages are intermittent, delayed, or out of range. Modules can talk most of the time, which is why the symptoms tend to come and go. The usual cause is intermittent wiring, a corroded connector, or a module that is starting to fail on that bus.

Medium

Can I keep driving? Usually yes, but expect intermittent glitches — warning lights and features cutting in and out — while a module or wiring problem degrades the bus.

Real-world scan data

Seen in

119

scans in the past year

Found in

<0.1%

of scans

<0.1%

of scans that found faults

Appears alongside · share of U0029 scans

U0100in 46.2% 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

Intermittent warning lights that come and go
Features on the bus work intermittently or respond slowly
Lost-communication codes that appear and then self-clear
A scan tool occasionally can't reach some modules

Common causes

Most likely first

Intermittent, corroded, or chafed bus wiring or connectorsLikely
A failing module intermittently disrupting the busCommon
Poor ground or unstable supply voltageCommon
Water or corrosion intrusion at a connectorLess often
Gateway module faultLess often

How to diagnose & fix

Work through it in order

Scan every module and note all U-codes, including pending and intermittent ones.
Wiggle-test the bus wiring and connectors while watching for dropouts.
Inspect and clean grounds and connector pins for corrosion.
Verify stable battery and charging voltage.
Isolate the offending module by disconnecting suspects; repair wiring or replace the confirmed module, then re-test.

FAQ

Quick answers

Is it safe to drive with U0029?+

Usually, but a degraded bus can intermittently disable features. If safety systems or warning lights are involved, have it diagnosed before relying on the car.

Can I just clear U0029?+

You can, but a 'performance' fault means the bus is still communicating poorly — the code returns until the wiring or module problem is fixed.

Read & clear U0029 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