U0034Vehicle Communication Bus A (-) Low
- Generic OBD-II code · Network
- How the car detects it
- U0034 flags the (-) wire of Vehicle Communication Bus A pulled toward ground. On a high-speed-type CAN, the layout Audi uses for the sensor/hybrid CAN behind this slot, that wire is CAN-Low, which normally drops by about a volt for dominant bits. onsemi found that with CAN-Low grounded, frames still pass, but the bus levels are distorted and the sending node draws more current, because its high-side driver now feeds the termination against ground. NXP lists this case among the hidden failures that go unnoticed without transceiver diagnosis. Expect intermittent errors or one module reporting the code rather than a dead network. No manufacturer documents U0034 publicly. A resistance near zero between CAN-Low and ground with the battery off confirms it.
- What you may notice
- Intermittent communication errors, vehicle mostly normal
- Code reported by a single module
- Likely causes
- Likely(-) wire insulation damaged and touching ground
- PossibleHarness pinched by a bracket or panel
- RareFaulty transceiver pulling the (-) line to ground
- Repair
- Hard · Usually a job for a workshop.Typical cost: €60 – €700
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.