Network, generic

U007B Control Module Communication Bus I Off

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

U007B is tied to no published manufacturer use; a Bus I only exists on vehicles split into many separate networks. The cause need not sit in the wiring at all. Onsemi describes a node whose transmit pin cannot produce a dominant level: every start-of-frame attempt fails and raises the error counter by eight, after 17 attempts it is error passive and shortly afterwards bus off, although the remaining bus may keep running normally. A damaged transceiver, a supply dip at the module or a cracked solder joint can therefore produce U007B in a single module only. If the code returns after clearing, check that module's power and ground under load and swap it against a known good unit before opening the harness.

Likely causes

Transceiver in the reporting module unable to drive the bus
Weak supply or ground at the reporting module
Short or open in the Bus I wiring

Symptoms

  • Only the reporting module's functions drop out
  • Code returns soon after clearing

Repair estimate

DifficultyHardWorkshop job
Parts and labour€80–1,000
Time0.5–4 h

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

Parts involved

bus i wiringcan transceiver

Related codes

U007AU007CU009BU009C

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