U0035Vehicle Communication Bus A (-) High
- Generic OBD-II code · Network
- Can trigger limp mode
- How the car detects it
- U0035 means the (-) wire of Vehicle Communication Bus A is held too high, typically shorted to battery voltage. On a two-wire high-speed-type CAN, such as Audi's sensor/hybrid CAN filed under Bus A, this is CAN-Low. onsemi's tests place CAN-Low at 12 V among the shorts that make transmission impossible: frames can no longer be sent and the controllers repeat them without success. All modules on Bus A drop out together, and units on other networks register their absence. This is the opposite of U0034, where traffic survives. No manufacturer documents U0035 publicly. Measuring CAN-Low against ground with ignition on shows battery voltage instead of roughly 1.5 to 2.5 V; chafing against a supply wire or a water-filled connector are the usual reasons.
- What you may notice
- All functions on Bus A fail together
- Lost-communication codes in modules on other networks
- Warning lamps or fallback modes depending on the modules involved
- Likely causes
- Likely(-) wire chafed against a battery or ignition feed
- PossibleWater in a connector linking the (-) wire to a supply pin
- RareDamaged transceiver driving the (-) line high
- Repair
- Hard · Usually a job for a workshop.Typical cost: €60 – €800
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.