Network, generic

U007A Control Module Communication Bus H Off

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

Bus H appears in no public manufacturer document for U007A; the code merely says that one module's CAN controller has switched to bus off on the network its maker labels H. A sensible check order follows from the physics. A high-speed CAN carries a 120 ohm resistor at each end, so with the battery disconnected the two wires should show roughly 60 ohms between them; about 120 ohms points to a missing terminator, near zero to the wires touching. With ignition on, a dominant bit pulls CAN-High toward 3.5 V and CAN-Low toward 1.5 V. As onsemi shows, a bus that is held recessive pushes a sender into bus off within a few dozen bit times, so shorts and transceiver damage come before software in the search.

Likely causes

Bus H wires shorted together
Terminating resistor open or a terminating module disconnected
Transceiver damaged, e.g. by overvoltage

Symptoms

  • Functions on Bus H fail or work only intermittently
  • 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 h wiringcan transceiver

Related codes

U0079U007BU0092U0093

References: en.wikipedia.org, onsemi.com, law.cornell.edu.