U0084Vehicle Communication Bus F (+) High
- Generic OBD-II code · Network
- How the car detects it
- U0084 is set when the (+) wire of Vehicle Communication Bus F carries too much voltage, typically after contact with battery power. For a FlexRay Bus F, as in Audi's A6/A7, the wire is bus plus (BP); NXP rates the bus pins of its TJA1081B to withstand shorts to 14, 24 and 48 V and caps the output current at about 72 mA, so the hardware usually survives while signal levels are wrong. If Bus F is a CAN, CAN-High at supply voltage is one of the faults that may leave traffic running: onsemi still saw frames pass, and NXP counts it among hidden failures that only a diagnosing transceiver reports. Volvo lists shorts of CAN-High to power behind its truck code U008088. No manufacturer documents U0084 itself. Look for wiring touching a feed or a wet connector.
- What you may notice
- Often no symptom, code found during a scan
- Sporadic dropouts of functions on Bus F
- Likely causes
- Likely(+) wire of Bus F touching a battery or ignition feed
- PossibleWater in a connector bridging the bus to a supply pin
- RareFaulty aftermarket wiring tapped into the bus
- 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.