Network, generic

U0098 Vehicle Communication Bus H (-) Low

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

U0098 is stored once the Bus H (-) wire, CAN-Low on a CAN, sits too low, normally from a short to ground. No manufacturer has made a use of U0098 public. With fault-tolerant low-speed CAN the short unfolds in stages: the receive pin of NXP's TJA1055 initially stays dominant without pause; once a time-out has passed, the chip disables its CANL driver and goes on receiving single-wire over CANH. Once the short is removed, normal levels return and the chip goes back to differential mode. Communication thus survives, but with less noise margin. A high-speed CAN also keeps running in this state, as onsemi measured, though with distorted levels. A resistance check of that wire against chassis, battery disconnected, confirms it.

Likely causes

(-) wire chafed to ground
Harness pinched by a fastener or panel
Faulty transceiver pulling the (-) line to ground

Symptoms

  • Usually no noticeable symptom
  • Occasional errors on Bus H in electrically noisy conditions

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 h wiringcan low wire

Related codes

U008FU0095U0097U0099

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