Network, generic

U0038 Vehicle Communication Bus B Performance

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

U0038 flags Vehicle Communication Bus B as present but unreliable: frames arrive late, incompletely or for a while not at all, rather than the bus being dead outright. Volkswagen's 2014 Touareg data book describes the trigger as a global time-out in which no messages come in any longer. Honda uses U0038 for the TM-CAN link between transmission and engine control: on 2016-17 Civic CVT models it appeared together with U0101 when an internal TCM fault cut the link, leaving the car stuck in Park without cranking and with several warning lamps lit. Honda replaces the TCM and on 2016 cars also updates the PCM software. Compared with U0037 the code describes a bus that still exists but whose traffic breaks off, so intermittent contacts, a failing node or software are the usual suspects.

Likely causes

Internal fault in a module on Bus B (Honda Civic: transmission control module)
Loose or corroded terminals interrupting traffic now and then
Software mismatch between modules on the bus

Symptoms

  • Selector stuck in Park, engine does not crank (Honda Civic CVT)
  • Several warning lamps on at once
  • Functions drop out intermittently

Repair estimate

DifficultyHardWorkshop job
Parts and labour€60–1,500
Time0.5–4 h

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

Parts involved

bus b wiringcontrol module

Related codes

U0029U0037U0047U0101

References: static.nhtsa.gov, static.nhtsa.gov, law.cornell.edu.