Network, generic

U008C Vehicle Communication Bus G (+) Low

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

U008C indicates a (+) wire on Vehicle Communication Bus G pulled too low, usually grounded. No manufacturer documents U008C publicly. On a high-speed CAN the (+) wire is CAN-High, which Texas Instruments describes as rising from about 2.5 V to 3.5 V for every dominant bit while CAN-Low drops to 1.5 V, giving the 2 V difference receivers decode. A grounded CAN-High cannot rise, so no node can assert a dominant bit; onsemi saw transmission fail outright in this state. Each failed frame raises the sender's error counter, so the same module may also log U0079 once it goes bus off. The whole network falls silent and other networks log the missing modules. With the battery disconnected, CAN-High showing only a few ohms to chassis confirms the short.

Likely causes

(+) wire of Bus G chafed against body metal
Harness pinched by a screw, panel or seat
Defective transceiver holding CAN-High to ground

Symptoms

  • All modules on Bus G drop out together
  • Many warnings and lost-communication codes at once

Repair estimate

DifficultyHardWorkshop job
Parts and labour€60–800
Time1–5 h

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

Parts involved

bus g wiringcan transceiver

Related codes

U0079U0089U008BU008DU0095

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