U0008High Speed CAN Communication Bus (-) High
- Generic OBD-II code · Network
- Can trigger limp mode
- How the car detects it
- U0008 means CAN-Low, the (-) wire of the high-speed CAN, is forced too high, typically through contact with the 12 V system or another supply rail. This fault blocks the bus: CAN-Low can no longer be driven down, no dominant state develops, and both onsemi and NXP found that transmission becomes impossible. Senders accumulate errors until they reach bus-off, so U0001 and lost-communication codes nearly always appear alongside, and engine, transmission or brake electronics may switch to stored default values. No manufacturer documents U0008 publicly. With ignition on, CAN-Low reading close to battery voltage instead of about 1.5 to 2.5 V confirms it; the contact point is usually where the bus pair runs beside a supply feed, for example after an accessory installation.
- What you may notice
- Total communication loss on the high-speed network
- Many warning lamps, possible no-start
- Scan tool cannot reach powertrain modules
- Likely causes
- LikelyCAN-Low chafed against a battery or ignition supply wire
- PossibleRetrofit wiring tapped into the bus pair by mistake
- RareBent pin or moisture linking CAN-Low to a supply contact
- Repair
- Hard · Usually a job for a workshop.Typical cost: €80 – €1,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.