U0002 code meaning
High Speed CAN Communication Bus Performance
Network system Generic code U00xx codes Check engine light
What U0002 means
U0002 stands for impaired rather than lost traffic on the high-speed CAN, and makers fill the slot in different ways. GM/Saab sets it when a supervised periodic message, which also tells the receiver that its sender is alive, has not shown up within the 250 ms supervision time; the receiver then carries on with a default value. FCA calls U0002 CAN C Bus Off Performance: a reflash for the 2013 Ram 2500/3500 6.7 L diesel PCM changed it from a one-trip to a two-trip MIL fault, whereas the 2024-26 Dodge Charger steering column module stores it without MIL because dips in supply voltage lasting about 40 ms trip a software bug. In contrast to U0001 the bus mostly keeps working, so complaints come and go: sporadic warnings or single functions dropping out briefly.
U0002 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyHard
- Typical labor0.5 to 6 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U0002
- Warning lamps that appear and disappear again
- Single functions briefly unavailable
- Code stored as history without a current fault
Common causes of U0002
- Most likelyIntermittent contact at connectors or splices of the bus pair
- PossibleModule software reacting to short voltage dips (reflash available)
- PossibleWeak battery or poor ground causing brief module resets
- Less likelyElectrical interference from retrofitted devices on the bus
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
CAN bus wiringControl module
What each part of U0002 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 02 | The exact fault in that area. |
What to do next
- Note U0002 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 U0002
What does U0002 mean?
U0002 means "High Speed CAN Communication Bus Performance". U0002 stands for impaired rather than lost traffic on the high-speed CAN, and makers fill the slot in different ways. It is a generic code, so it means the same on every make.
Is it safe to drive with U0002?
Drive gently and only to a workshop. With U0002 the car can go into limp mode (reduced power) to protect itself.
Will U0002 fail an emissions test?
Yes, it can. U0002 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is U0002 to fix?
Difficulty: hard. A typical repair takes 0.5 to 6 hours of work. This is a job for a workshop.
Will U0002 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.