Network, generic

U0090 Vehicle Communication Bus G (-) High

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

U0090 is logged when Bus G's (-) wire is pulled up, typically by a short to a supply feed; in CAN terms this is the CAN-Low line. U0090 is not described in any public manufacturer source. Unlike a grounded CAN-Low, this fault normally stops the bus: onsemi found transmission impossible with CAN-Low at 12 V, and NXP rates it as a short under which communication fails. The search is easier once you know which feed is involved. Nissan's CAN diagnostic chart measures each bus wire to ground both with the key off and with it on, and keeps separate entries for shorts to battery and to an ignition feed. A fault that is present only with the ignition on points to a switched circuit, one that persists with the key off to a permanent battery feed.

Likely causes

(-) wire shorted to a permanent battery feed
(-) wire touching a switched ignition feed in the harness
Retrofitted equipment spliced into the bus wires

Symptoms

  • All modules on Bus G stop responding at once
  • Warning lamps and lost-communication codes in several systems
  • Fault may come and go with the ignition switch position

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 low wire

Related codes

U0079U008DU008FU0091U0099

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