U0029
Vehicle Communication Bus A Performance
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.
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.
Related codes
Often seen with U0029
Read & clear U0029 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