U0047 code meaning
Vehicle Communication Bus C Performance
What U0047 means
U0047 says that Vehicle Communication Bus C is up but its traffic is not dependable, for instance through sporadic error frames, messages arriving too late or brief dropouts. CAN controllers keep score with error counters: as onsemi explains with reference to ISO 11898-1, every failed transmission adds eight to the transmit counter, beyond about 128 the node turns error passive and past 255 it takes itself off the bus, rejoining only after 128 runs of eleven recessive bits. A performance code is typically set somewhere along that path, before or between short bus-off episodes. No manufacturer documents U0047 publicly; CARB only requires faults in digital communication to be detected and stored separately. Loose terminals, corroded connectors, interference and a node that resets now and then are the usual causes.
U0047 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyHard
- Typical labor0.5 to 5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U0047
- Functions drop out briefly and return
- Sporadic warning messages from several systems
Common causes of U0047
- Most likelyLoose or corroded terminals on Bus C
- PossibleA module on Bus C resetting because of weak supply or ground
- Less likelyInterference coupled into the bus wiring
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Bus c wiringControl module
What each part of U0047 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 47 | The exact fault in that area. |
What to do next
- Note U0047 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 U0047
What does U0047 mean?
U0047 means "Vehicle Communication Bus C Performance". U0047 says that Vehicle Communication Bus C is up but its traffic is not dependable, for instance through sporadic error frames, messages arriving too late or brief dropouts. It is a generic code, so it means the same on every make.
Is it safe to drive with U0047?
U0047 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will U0047 fail an emissions test?
U0047 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 U0047 to fix?
Difficulty: hard. A typical repair takes 0.5 to 5 hours of work. This is a job for a workshop.
Will U0047 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.