U0008 code meaning
High Speed CAN Communication Bus (-) High
What U0008 means
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.
U0008 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyHard
- Typical labor1 to 6 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U0008
- Total communication loss on the high-speed network
- Many warning lamps, possible no-start
- Scan tool cannot reach powertrain modules
Common causes of U0008
- Most likelyCAN-Low chafed against a battery or ignition supply wire
- PossibleRetrofit wiring tapped into the bus pair by mistake
- Less likelyBent pin or moisture linking CAN-Low to a supply contact
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
CAN low wireModule connector
What each part of U0008 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 08 | The exact fault in that area. |
What to do next
- Note U0008 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about U0008
What does U0008 mean?
U0008 means "High Speed CAN Communication Bus (-) High". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with U0008?
Drive gently and only to a workshop. With U0008 the car can go into limp mode (reduced power) to protect itself.
Will U0008 fail an emissions test?
U0008 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is U0008 to fix?
Difficulty: hard. A typical repair takes 1 to 6 hours of work. This is a job for a workshop.
Will U0008 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.