Network, generic

U0047 Vehicle Communication Bus C Performance

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

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.

Likely causes

Loose or corroded terminals on Bus C
A module on Bus C resetting because of weak supply or ground
Interference coupled into the bus wiring

Symptoms

  • Functions drop out briefly and return
  • Sporadic warning messages from several systems

Repair estimate

DifficultyHardWorkshop job
Parts and labour€60–800
Time0.5–5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

bus c wiringcontrol module

Related codes

U0002U0029U0038U0046

References: onsemi.com, law.cornell.edu, nxp.com.