Network, generic

U0066 Vehicle Communication Bus E (+) Open

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

U0066 indicates a break in the (+) wire of Vehicle Communication Bus E. Where Bus E is a two-wire CAN, like the infotainment CAN Audi and Volkswagen monitor under that slot, the (+) wire is CAN-High. The physical layer decides how visible the fault is. With fault-tolerant low-speed hardware, NXP's TJA1055 rides through a CAN-High interruption with drivers, termination and differential receiver left as they were, and only counts edges: once CAN-High and CAN-Low differ by four pulses, its error output goes low. A high-speed transceiver offers no such check, so modules notice only that partners beyond the break fall silent. No manufacturer documents U0066 publicly; Audi's A3 case of a badly seated contact carrier in a multi-pin connector shows how such interruptions arise.

Likely causes

(+) wire of Bus E broken in the harness
Contact carrier or terminal not seated in a multi-pin connector
Connector left unplugged after a repair

Symptoms

  • Modules beyond the break, often infotainment units, unreachable
  • Lost-communication codes for individual modules

Repair estimate

DifficultyHardWorkshop job
Parts and labour€60–700
Time0.5–5 h

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

Parts involved

bus e wiringmodule connector

Related codes

U0039U0057U0064U0067U0069

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