Network, generic

U0036 Vehicle Communication Bus A (-) Shorted to Bus A (+)

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

U0036 describes a short between the (+) and (-) wires of Vehicle Communication Bus A. On a CAN-type bus the differential voltage then stays at zero, receivers see only recessive bits and, as onsemi's measurements on high-speed CAN show, no frame can be sent any more; NXP adds that transceiver diagnosis cannot detect this short. Audi documents U003600 under exactly its J2012 name for the 2018-21 Q5 plug-in hybrid: together with U002800, U002900 and drive-motor and power-electronics codes it appears when the 12 V harness of the power electronics chafes against the underbody trim, with warning lamps and in some cases a car that cannot be driven. The fix is repairing the wires and rerouting the harness. With the battery off, near zero ohms between the bus wires confirms the short.

Likely causes

Harness chafed so that both bus wires touch (Audi Q5 PHEV: underbody trim)
Water in a splice or connector bridging the two wires
Damaged transceiver shorting its bus pins

Symptoms

  • Several warning lamps on at once
  • Vehicle may refuse to drive (Audi Q5 PHEV)
  • Drive-motor and power-electronics codes stored alongside

Repair estimate

DifficultyHardWorkshop job
Parts and labour€80–1,000
Time1–6 h

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

Parts involved

bus a wiring

Related codes

U0009U0027U0028U0029U0110

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