Network, generic

U0087 Vehicle Communication Bus F (-) High

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

U0087 stands for a (-) wire on Vehicle Communication Bus F pulled too high, most often through contact with battery voltage. If Bus F is the FlexRay of an Audi A6/A7, the wire is bus minus (BM); held above BP, it creates a constant negative difference that receivers treat as DATA_0, so the channel looks permanently busy and no node can place a frame. NXP's TJA1081B tolerates such a short on its bus pins without damage. On a CAN, CAN-Low at supply voltage cannot be pulled down for a dominant bit; onsemi and NXP both describe the bus as blocked. Volvo includes a short of CAN-Low to power among the causes of its truck code U008088. No manufacturer documents U0087 itself. With ignition on, a (-) wire near battery voltage confirms the fault.

Likely causes

(-) wire of Bus F shorted to a battery or ignition feed
Moisture in a connector linking the (-) pin to a supply
Internally shorted transceiver in one module

Symptoms

  • All functions on Bus F fail together
  • Warning lamps and messages from several systems

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 f wiringcan transceiver

Related codes

U0071U0080U0084U0086

References: nxp.com, onsemi.com, nxp.com, static.nhtsa.gov.